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; ============================================================================
;        __
;   \\__/ o\    (C) 2015  Robert Finch, Stratford
;    \  __ /    All rights reserved.
;     \/_//     robfinch@finitron.ca
;       ||
;
;
; This source file is free software: you can redistribute it and/or modify
; it under the terms of the GNU Lesser General Public License as published
; by the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This source file is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program.  If not, see .
;
; ============================================================================
;
 
SCRSZ   EQU     2604
CR      EQU     0x0D            ;ASCII equates
LF      EQU     0x0A
TAB     EQU     0x09
CTRLC   EQU     0x03
BS              EQU     0x07
CTRLH   EQU     0x08
CTRLI   EQU     0x09
CTRLJ   EQU     0x0A
CTRLK   EQU     0x0B
CTRLM   EQU 0x0D
CTRLS   EQU     0x13
CTRLX   EQU     0x18
XON             EQU     0x11
XOFF    EQU     0x13
ESC             EQU     0x1B
 
SC_LSHIFT       EQU             $12
SC_RSHIFT       EQU             $59
SC_KEYUP        EQU             $F0
SC_EXTEND       EQU             $E0
SC_CTRL         EQU             $14
SC_ALT          EQU             $11
SC_DEL          EQU             $71             ; extend
SC_LCTRL        EQU             $58
SC_NUMLOCK      EQU             $77
SC_SCROLLLOCK   EQU     $7E
SC_CAPSLOCK     EQU             $58
 
E_BadFuncno    EQU       1
BIOS_E_Timeout EQU       2
E_Unsupported  EQU       3
 
BIOS_STACKTOP           EQU             $3bf8
INT_STACK                       EQU             $37f8
VIDEO_BIOS_STACKTOP     EQU             $3ff8
 
IOBASE_ADDR     EQU             0xFFD00000
IOLMT           EQU             0x100000
LEDS            EQU             0xC0600
TEXTSCR         EQU             0x00000
TEXTSCR2        EQU             0x10000
TEXTREG         EQU             0xA0000
TEXTREG2        EQU             0xA0040
TEXT_COLS       EQU             0x0
TEXT_ROWS       EQU             0x2
TEXT_CURPOS     EQU             0x16
KEYBD           EQU             0xC0000
 
PIC_IS          EQU             0xC0FC0
PIC_IE          EQU             0xC0FC8
PIC_ES          EQU             0xC0FE0
PIC_ESR         EQU             0xC0FE8         ; edge sense reset
 
                bss
                org             $0000
                dw              0                                ; the first word is unused
Milliseconds    dw              0
m_w                             dh              0
m_z                             dh              0
KeyState1               db              0
KeyState2               db              0
KeybdLEDs               db              0
KeybdWaitFlag   db              0
 
CursorX                 dc              0
CursorY                 dc              0
VideoPos                dc              0
                align   4
NormAttr                dh              0
Vidregs                 dh              0
Vidptr                  dh              0
EscState                dc              0
Textrows                dc              0
Textcols                dc              0
                align   8
reg_save                fill.w  64,0
creg_save               fill.w  16,0
sreg_save               fill.w  16,0
preg_save               dw              0
 
                bss
                org             $4000
 
 
rxfull     EQU      1
Uart_ms         db      0
Uart_txxonoff   db      0
Uart_rxhead     dc      0
Uart_rxtail     dc      0
Uart_rxflow     db      0
Uart_rxrts      db      0
Uart_rxdtr      db      0
Uart_rxxon      db      0
Uart_foff       dc      0
Uart_fon        dc      0
Uart_txrts      db      0
Uart_txdtr      db      0
Uart_txxon      db      0
Uart_rxfifo     fill.b  512,0
 
NUMWKA          fill.b  64,0
 
        code 17 bits
        org             $FFFF8000
 
cold_start:
                ; Initialize segment registers for flat model
                mtspr   zs,r0
                ldis    zs.lmt,#-1
                mtspr   ds,r0
                ldis    ds.lmt,#-1
                mtspr   es,r0
                ldis    es.lmt,#-1
                mtspr   fs,r0
                ldis    fs.lmt,#-1
                mtspr   gs,r0
                ldis    gs.lmt,#-1
                ldis    hs,#IOBASE_ADDR
                ldis    hs.lmt,#IOLMT
 
                ; set SS:SP
                mtspr   ss,r0
                ldis    ss.lmt,#$4000
                ldi             r31,#$03ef8             ; initialize kernel SP
                ldi             r27,#$03bf8             ; initialize SP
 
                ; switch processor to full speed
                stp             #$FFFF
 
                ; set interrupt table at $1000
                ldis    c12,#$1000
 
                ; set all vectors to the uninitialized interrupt vector
                mov             r4,r0
                ldis    lc,#255         ; 256 vectors to set
su1:
                ldi             r1,#uii_jmp
                mov             r2,r4
                bsr             set_vector      ; trashes r2,r3
                addui   r4,r4,#1
                loop    su1
 
                ; setup break vector
                lla             r1,cs:brk_jmp
                ldi             r2,#0
                bsr             set_vector
 
                ; setup Video BIOS vector
                lla             r1,cs:vb_jmp
                ldi             r2,#10
                bsr             set_vector
 
                ; setup NMI vector
                lla             r1,cs:nmi_jmp
                ldi             r2,#254
                bsr             set_vector
 
                lla             r1,cs:svc_jmp
                ldi             r2,#190
                bsr             set_vector
                lla             r1,cs:rsc_jmp
                ldi             r2,#191
                bsr             set_vector
 
                ; spurious interrupt
                ;
                lla             r1,cs:spur_jmp
                ldi             r2,#192
                bsr             set_vector
 
                ; setup MSI vector
                sh              r0,Milliseconds
                lla             r1,cs:msi_jmp
                ldi             r2,#193
                bsr             set_vector
 
                ; setup IRQ vector
                lla             r1,cs:tms_jmp
                ldi             r2,#194
                bsr             set_vector
 
                ; setup BTNU vector
                lla             r1,cs:btnu_jmp
                ldi             r2,#200
                bsr             set_vector
 
                ; setup KM vector
                lla             r1,cs:km_jmp
                ldi             r2,#245
                bsr             set_vector
 
                ; setup data bus error vector
                lla             r1,cs:dbe_jmp
                ldi             r2,#251
                bsr             set_vector
 
                ; Initialize PIC
                ldi             r1,#%00000111           ; time slice interrupt is edge sensitive
                sh              r1,hs:PIC_ES
                ldi             r1,#%100000111          ; enable time slice interrupt, msi, nmi
                sh              r1,hs:PIC_IE
 
                ; Initialize random number generator
                ; m_z and m_w must not be zero
                ldi             r1,#$88888888
                sh              r1,m_w
                ldi             r1,#$77777777
                sh              r1,m_z
 
                mov             r1,r0
                mov             r2,r0
                mov             r3,r0
                mov             r4,r0
                mov             r5,r0
 
                ldi             r1,#1
                sc              r1,hs:LEDS
 
                tlbwrreg DMA,r0                         ; clear TLB miss registers
                tlbwrreg IMA,r0
                ldi                     r1,#2                   ; 2 wired registers
                tlbwrreg        Wired,r1
                ldi                     r1,#$2                  ; 64kiB page size
                tlbwrreg        PageSize,r1
 
                ; setup the first translation
                ; virtual page $FFFF0000 maps to physical page $FFFF0000
                ; This places the BIOS ROM at $FFFFxxxx in the memory map
                ldi                     r1,#$80000101   ; ASID=zero, G=1,valid=1
                tlbwrreg        ASID,r1
                ldi                     r1,#$0FFFF
                tlbwrreg        VirtPage,r1
                tlbwrreg        PhysPage,r1
                tlbwrreg        Index,r0                ; select way #0
                tlbwi                                           ; write to TLB entry group #0 with hold registers
 
                ; setup second translation
                ; virtual page 0 maps to physical page 0
                ldi                     r1,#$80000101   ; ASID=zero, G=1,valid=1
                tlbwrreg        ASID,r1
                tlbwrreg        VirtPage,r0
                tlbwrreg        PhysPage,r0
                ldi                     r1,#8                   ; select way#1
                tlbwrreg        Index,r1
                tlbwi                                           ; write to TLB entry group #0 with hold registers
 
                ; turn on the TLB
;               tlben
 
                ; enable maskable interrupts
                ; Interrupts also are not enabled until an RTI instruction is executed.
                ; there will likely be a timer interrupt outstanding so this
                ; should go to the timer IRQ.
                cli
 
                ; now globally enable interrupts using the RTI instruction, this will also
                ; switch to core to application/user mode.
                ldis    c14,#j1                 ; c14 contains RTI return address
                sync
                rti
j1:
                ldi             r1,#2
                sc              r1,hs:LEDS
                sb              r0,EscState
                bsr             SerialInit
;               bsr             Debugger
                ldi             r2,#msgStartup
                ldis    lc,#msgStartupEnd-msgStartup-1
j3:
;               lbu             r1,[r2]
;               addui   r2,r2,#1
;               tst             p0,r1
;p0.eq  br              j2
;               bsr             SerialPutChar
;               loop    j3
j2:
                bsr             VideoInit
                bsr             VBClearScreen
;               bsr             VBClearScreen2
                ldi             r1,#3
                sc              r1,hs:LEDS
                mov             r1,r0
                mov             r2,r0
                ldi             r6,#2           ; Set Cursor Pos
                sys             #10
                ldi             r1,#6
                sc              r1,hs:LEDS
                bsr             alphabet
                lla             r1,cs:msgStartup        ; convert to linear address
                ldi             r6,#$14
                sys             #10
 
;------------------------------------------------------------------------------
;------------------------------------------------------------------------------
; Monitor
;------------------------------------------------------------------------------
;------------------------------------------------------------------------------
 
Monitor:
                lla             r1,cs:msgMonitor
                bsr             VBDisplayString
 
                ; Display monitor prompt
.prompt:
                ldi             r1,#CR
                bsr             VBDisplayChar
                ldi             r1,#LF
                bsr             VBDisplayChar
                ldi             r1,#'$'
                bsr             VBDisplayChar
                bsr             CursorOn
.getkey:
                bsr             KeybdGetCharWait
                bsr             VBDisplayChar
                cmpi    p0,r1,#CR
p0.ne   br              .getkey
                bsr             CursorOff
                lcu             r1,CursorY
                lcu             r7,Textcols
                mtspr   lc,r7                           ; use loop counter as safety
                mulu    r10,r1,r7                       ; pos = row * cols
                _4addu  r10,r10,r0                      ; pos *= 4
.0001:
                bsr             MonGetch1                       ; get character skipping spaces
                cmpi    p0,r1,#'$'                      ; skip over prompt
p0.eq   br              .0001
                cmpi    p0,r1,#'d'                      ; debug ?
p0.eq   bsr             Debugger
                cmpi    p0,r1,#'g'
p0.eq   bsr             GoGraphics
                cmpi    p0,r1,#'t'
p0.eq   bsr             MonGetch
p0.eq   cmpi    p0,r1,#'x'
p0.eq   bsr             GoText
                cmpi    p0,r1,'r'
p0.eq   bsr             RandomDots
                cmpi    p0,r1,#'c'
p0.eq   bsr             VBClearScreen
p0.eq   mov             r1,r0
p0.eq   mov             r2,r0
p0.eq   ldi             r6,#2
p0.eq   sys             #10
                br              .prompt
 
;------------------------------------------------------------------------------
; Returns:
;       r1  ascii code for character
;       r10 incremented
;   lc  decremented
;------------------------------------------------------------------------------
 
MonGetch:
                addui   r31,r31,#-8
                sws             c1,[r31]
                lhu             r1,hs:[r10]
                andi    r1,r1,#$3ff
                bsr             VBScreenToAscii
                addui   r10,r10,#4
                loop    .0001                   ; decrement loop counter
.0001:
                lws             c1,[r31]
                addui   r31,r31,#8
                rts
 
;------------------------------------------------------------------------------
; Returns:
;       r1  ascii code for character
;       r10 incremented by number of spaces + 1
;   lc  decremented by number of spaces + 1
;------------------------------------------------------------------------------
 
MonGetch1:
                addui   r31,r31,#-8
                sws             c1,[r31]
.0001:
                lhu             r1,hs:[r10]
                andi    r1,r1,#$3ff
                bsr             VBScreenToAscii
                addui   r10,r10,#4
                cmpi    p0,r1,#' '
p0.leu  loop    .0001
                lws             c1,[r31]
                addui   r31,r31,#8
                rts
 
;------------------------------------------------------------------------------
;------------------------------------------------------------------------------
 
GoGraphics:
                lhu             r3,Vidregs
                ldi             r1,#4
                sc              r1,Textrows
                sh              r1,hs:4[r3]             ; # rows
                ldi             r1,#720
                sh              r1,hs:12[r3]    ; window top
                rts
 
GoText:
                lhu             r3,Vidregs
                ldi             r1,#31
                sc              r1,Textrows
                sh              r1,hs:4[r3]             ; # rows
                ldi             r1,#17
                sh              r1,hs:12[r3]    ; window top
                rts
 
// ----------------------------------------------------------------------------
// Uses George Marsaglia's multiply method
//
// m_w = ;    /* must not be zero */
// m_z = ;    /* must not be zero */
//
// uint get_random()
// {
//     m_z = 36969 * (m_z & 65535) + (m_z >> 16);
//     m_w = 18000 * (m_w & 65535) + (m_w >> 16);
//     return (m_z << 16) + m_w;  /* 32-bit result */
// }
// ----------------------------------------------------------------------------
//
gen_rand:
                addui   r31,r31,#-8
                sw              r2,[r31]
                lhu             r1,m_z
                mului   r2,r1,#36969
                shrui   r1,r1,#16
                addu    r2,r2,r1
                sh              r2,m_z
 
                lhu             r1,m_w
                mului   r2,r1,#18000
                shrui   r1,r1,#16
                addu    r2,r2,r1
                sh              r2,m_w
rand:
                lhu             r1,m_z
                shli    r1,r1,#16
                addu    r1,r1,r2
                lw              r2,[r31]
                addui   r31,r31,#8
                rts
 
// ----------------------------------------------------------------------------
// Display random dots on the graphics screen.
// ----------------------------------------------------------------------------
 
RandomDots:
                addui   r31,r31,#-8
                sws             c1,[r31]
                mov             r4,r0
.0001:
                bsr             gen_rand                ; get random bitmap memory location
                modu    r2,r1,#172032   ; mod the memory size
                shli    r2,r2,#1                ; *2 for 16 bit data
                bsr             gen_rand                ; get random color
                modui   r3,r1,#$1000    ; limit to 12 bits
                sc              r3,zs:$FFA00000[r2]     ; store color in memory
                addui   r4,r4,#1                ; increment loop index
                andi    r4,r4,#$FFF             ;
                tst             p0,r4                   ; check if time to check for keypress
p0.eq   bsr             KeybdGetCharNoWait      ; try get a key, but don't wait
                tst             p0,r1                   ; branch if no key pressed
p0.lt   br              RandomDots.0001
                lws             c1,[r31]
                addui   r31,r31,#8
                rts
 
;------------------------------------------------------------------------------
 
msgStartup:
                byte    "Thor Test System Starting...",CR,LF,0
msgStartupEnd:
msgMonitor:
                byte    CR,LF
                byte    "d  - run debugger",CR,LF
                byte    "g  - graphics mode",CR,LF
                byte    "tx - text mode",CR,LF
                byte    "r  - random dots",CR,LF
                byte    0
 
bad_ram:
                ldi             r1,#'B'
                bsr             VBAsciiToScreen
                ori             r1,r1,#%011000000_111111111_00_00000000
                sh              r1,hs:TEXTSCR+16
.bram1: br              .bram1
 
;------------------------------------------------------------------------------
; alphabet:
;
; Display the alphabet across the top of the screen.
;------------------------------------------------------------------------------
 
alphabet:
                addui   sp,sp,#-8
                sws             c1,[sp]                 ; store off return address
                ldi             r5,#'A'                 ; the first char
                ldi             r3,#TEXTSCR             ; screen address
                ldis    lc,#25                  ; 25 chars
.0001:
                mov             r1,r5                   ; r1 = ascii letter
                bsr             VBAsciiToScreen ; r1 = screen char
                lhu             r2,NormAttr             ; r2 = attribute
                or              r1,r1,r2                ; r1 = screen char + attribute
                sh              r1,hs:[r3]              ; store r1 to screen
                addui   r5,r5,#1                ; increment to next char
                addui   r3,r3,#4                ; increment to next screen loc
                loop    .0001                   ; loop back
                lws             c1,[sp]                 ; restore return address
                addui   sp,sp,#8
                rts
 
;------------------------------------------------------------------------------
; Set interrupt vector
;
; Parameters:
;       r1 = linear address of jump code
;       r2 = vector number to set
; Trashes: r2,r3,r5,p0
;------------------------------------------------------------------------------
 
set_vector:
                mfspr   r3,c12                  ; get base address of interrupt table
                _16addu r2,r2,r3
                lh              r3,zs:[r1]
                cmpi    p0,r3,#$003F6F01        ; unitialized interrupt number load
p0.eq   shli    r5,r2,#18
p0.eq   or              r3,r3,r5
                sh              r3,zs:[r2]
                lh              r3,zs:4[r1]
                sh              r3,zs:4[r2]
                lh              r3,zs:8[r1]
                sh              r3,zs:8[r2]
                lh              r3,zs:12[r1]
                sh              r3,zs:12[r2]
                rts
 
;------------------------------------------------------------------------------
; Save the register context.
;
; Parameters:
;       DS points to app's data space
;
;------------------------------------------------------------------------------
 
save_context:
                sw              r1,reg_save+8*1
                sw              r2,reg_save+8*2
                sw              r3,reg_save+8*3
                sw              r4,reg_save+8*4
                sw              r5,reg_save+8*5
                sw              r6,reg_save+8*6
                sw              r7,reg_save+8*7
                sw              r8,reg_save+8*8
                sw              r9,reg_save+8*9
                sw              r10,reg_save+8*10
                sw              r11,reg_save+8*11
                sw              r12,reg_save+8*12
                sw              r13,reg_save+8*13
                sw              r14,reg_save+8*14
                sw              r15,reg_save+8*15
                sw              r16,reg_save+8*16
                sw              r17,reg_save+8*17
                sw              r18,reg_save+8*18
                sw              r19,reg_save+8*19
                sw              r20,reg_save+8*20
                sw              r21,reg_save+8*21
                sw              r22,reg_save+8*22
                sw              r23,reg_save+8*23
                sw              r24,reg_save+8*24
                sw              r25,reg_save+8*25
                sw              r26,reg_save+8*26
                sw              r27,reg_save+8*27
                sw              r28,reg_save+8*28
                sw              r29,reg_save+8*29
                sw              r30,reg_save+8*30
                sw              r31,reg_save+8*31
                sws             ds,sreg_save+8*1
                sws             es,sreg_save+8*2
                sws             fs,sreg_save+8*3
                sws             gs,sreg_save+8*4
                sws             hs,sreg_save+8*5
                sws             ss,sreg_save+8*6
                sws             cs,sreg_save+8*7
                sws             ds.lmt,sreg_save+8*9
                sws             es.lmt,sreg_save+8*10
                sws             fs.lmt,sreg_save+8*11
                sws             gs.lmt,sreg_save+8*12
                sws             hs.lmt,sreg_save+8*13
                sws             ss.lmt,sreg_save+8*14
                sws             cs.lmt,sreg_save+8*15
                sws             c1,creg_save+8*1
                sws             c2,creg_save+8*2
                sws             c3,creg_save+8*3
                sws             c4,creg_save+8*4
                sws             c5,creg_save+8*5
                sws             c6,creg_save+8*6
                sws             c7,creg_save+8*7
                sws             c8,creg_save+8*8
                sws             c9,creg_save+8*9
                sws             c10,creg_save+8*10
                sws             c11,creg_save+8*11
                sws             c13,creg_save+8*13
                sws             c14,creg_save+8*14
                sws             pregs,preg_save
                rte
 
;------------------------------------------------------------------------------
; Restore register context.
; Parameters:
;       DS points to app's data space.
;------------------------------------------------------------------------------
 
restore_context:
                lw              r1,reg_save+8*1
                lw              r2,reg_save+8*2
                lw              r3,reg_save+8*3
                lw              r4,reg_save+8*4
                lw              r5,reg_save+8*5
                lw              r6,reg_save+8*6
                lw              r7,reg_save+8*7
                lw              r8,reg_save+8*8
                lw              r9,reg_save+8*9
                lw              r10,reg_save+8*10
                lw              r11,reg_save+8*11
                lw              r12,reg_save+8*12
                lw              r13,reg_save+8*13
                lw              r14,reg_save+8*14
                lw              r15,reg_save+8*15
                lw              r16,reg_save+8*16
                lw              r17,reg_save+8*17
                lw              r18,reg_save+8*18
                lw              r19,reg_save+8*19
                lw              r20,reg_save+8*20
                lw              r21,reg_save+8*21
                lw              r22,reg_save+8*22
                lw              r23,reg_save+8*23
                lw              r24,reg_save+8*24
                lw              r25,reg_save+8*25
                lw              r26,reg_save+8*26
                lw              r27,reg_save+8*27
                lw              r28,reg_save+8*28
                lw              r29,reg_save+8*29
                lw              r30,reg_save+8*30
                lw              r31,reg_save+8*31
;               lws             ds,sreg_save+8*1
                lws             es,sreg_save+8*2
                lws             fs,sreg_save+8*3
                lws             gs,sreg_save+8*4
                lws             hs,sreg_save+8*5
                lws             ss,sreg_save+8*6
                lws             cs,sreg_save+8*7
;               lws             ds.lmt,sreg_save+8*9
                lws             es.lmt,sreg_save+8*10
                lws             fs.lmt,sreg_save+8*11
                lws             gs.lmt,sreg_save+8*12
                lws             hs.lmt,sreg_save+8*13
                lws             ss.lmt,sreg_save+8*14
                lws             cs.lmt,sreg_save+8*15
                lws             c1,creg_save+8*1
                lws             c2,creg_save+8*2
                lws             c3,creg_save+8*3
                lws             c4,creg_save+8*4
                lws             c5,creg_save+8*5
                lws             c6,creg_save+8*6
                lws             c7,creg_save+8*7
                lws             c8,creg_save+8*8
                lws             c9,creg_save+8*9
                lws             c10,creg_save+8*10
                lws             c11,creg_save+8*11
;               lws             c13,creg_save+8*13
                lws             c14,creg_save+8*14
                lws             pregs,preg_save
                rte
 
.include "video.asm"
.include "keyboard.asm"
.include "serial.asm"
.include "debugger.asm"
 
 
;------------------------------------------------------------------------------
; BTNU IRQ routine.
;
;------------------------------------------------------------------------------
;
btnu_rout:
                sync
                addui   r31,r31,#-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ; update on-screen IRQ live indicator
                lh              r1,hs:TEXTSCR+312
                addui   r1,r1,#1
                sh              r1,hs:TEXTSCR+312
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                addui   r31,r31,#16
                sync
                rti
 
;------------------------------------------------------------------------------
;------------------------------------------------------------------------------
 
spur_rout:
                sync
                ldi             r31,#INT_STACK-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
;               ldi             r1,#18
;               sc              r1,hs:LEDS
 
                ; update on-screen IRQ live indicator
                lh              r1,hs:TEXTSCR+316
                addui   r1,r1,#1
                sh              r1,hs:TEXTSCR+316
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                sync
                rti
 
;------------------------------------------------------------------------------
; Uninitialized interrupt
;------------------------------------------------------------------------------
uii_rout:
                sync
                ldi             r31,#INT_STACK-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ; update on-screen IRQ live indicator
                ldi             r1,#'U'|%011000000_111111111_00_00000000
                sh              r1,hs:TEXTSCR+320
 
                mov             r5,r63
                sc              r63,hs:LEDS
                bsr             DisplayAddr
 
                ldi             r6,#2
                ldi             r2,#0
                ldi             r7,#0
.0001:
                ldis    60,#18          ; set breakout index to 18
                sync
                mtspr   61,r7           ; select history reg #
                sync
                ldis    60,#16          ; set breakout index to 16
                sync
                mfspr   r5,61           ; get address
                bsr             DisplayAddr
                addui   r2,r2,#1
                ldis    60,#17          ; set breakout index to 17
                sync
                mfspr   r5,61           ; get address
                bsr             DisplayAddr
                addui   r2,r2,#1
                addui   r7,r7,#1
                cmpi    p0,r7,#63
p0.ltu  br              .0001
 
uii_hang:
                br              uii_hang
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                sync
                rti
 
;------------------------------------------------------------------------------
; Non-maskable interrupt routine.
;
;------------------------------------------------------------------------------
;
nmi_rout:
                sync
                ldi             r31,#INT_STACK-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ldi             r1,#16
                sc              r1,hs:LEDS
 
                ; reset the edge sense circuit to re-enable interrupts
                ldi             r1,#0
                sh              r1,hs:PIC_ESR
 
                ; update on-screen IRQ live indicator
                lh              r1,hs:TEXTSCR+324
                addui   r1,r1,#1
                sh              r1,hs:TEXTSCR+324
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                sync
                rti
 
;------------------------------------------------------------------------------
; Millisecond (1024 Hz) interrupt routine.
;
;------------------------------------------------------------------------------
;
msi_rout:
                sync
                addui   r31,r31,#-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ldi             r1,#24
                sc              r1,hs:LEDS
 
                ; reset the edge sense circuit to re-enable interrupts
                ldi             r1,#1
                sh              r1,hs:PIC_ESR
 
                ; update milliseconds
                lh              r1,zs:Milliseconds
                addui   r1,r1,#1
                sh              r1,zs:Milliseconds
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                addui   r31,r31,#16
                sync
                rti
 
;------------------------------------------------------------------------------
; Time Slice IRQ routine.
;
;------------------------------------------------------------------------------
;
tms_rout:
                sync
                addui   r31,r31,#-16
                sw              r1,[r31]
                sws             hs,8[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ldi             r1,#32
                sc              r1,hs:LEDS
 
                ; reset the edge sense circuit to re-enable interrupts
                ldi             r1,#2
                sh              r1,hs:PIC_ESR
 
                ; update on-screen IRQ live indicator
                lh              r1,hs:TEXTSCR+328
                addui   r1,r1,#1
                sh              r1,hs:TEXTSCR+328
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                addui   r31,r31,#16
                sync
                rti
 
;------------------------------------------------------------------------------
; Data bus error routine.
;
;
;------------------------------------------------------------------------------
;
dbe_rout:
                sync
                ldi             r31,#INT_STACK-24
                sw              r1,[r31]
                sws             hs,8[r31]
                sw              r5,16[r31]
 
                ; set I/O segment
                ldis    hs,#$FFD00000
 
                ldi             r1,#64
                sc              r1,hs:LEDS
 
                ; reset the bus error circuit to re-enable interrupts
                sh              r0,hs:$CFFE0
 
                ; update on-screen DBE indicator
                ldi             r1,'D'|%011000000_000000110_0000000000
                sh              r1,hs:TEXTSCR+320
 
                ; Advance the program to the next address
                mfspr   r5,c14
                bsr             DBGGetInsnLength
                addu    r1,r5,r1
                mtspr   c14,r1
 
                ; restore regs and return
                lw              r1,[r31]
                lws             hs,8[r31]
                lw              r5,16[r31]
                sync
                rti
 
;------------------------------------------------------------------------------
; Break routine
;
; Currently uses only registers in case memory is bad, and sets an indicator
; on-screen.
;------------------------------------------------------------------------------
;
brk_rout:
                sync
                ldi             r1,#'B'
                bsr             VBAsciiToScreen
                ori             r1,r1,#|%011000000_111111111_00_00000000
                sh              r1,zs:$FFD10140
                ldi             r1,#'R'
                bsr             VBAsciiToScreen
                ori             r1,r1,#|%011000000_111111111_00_00000000
                sh              r1,zs:$FFD10144
                ldi             r1,#'K'
                bsr             VBAsciiToScreen
                ori             r1,r1,#|%011000000_111111111_00_00000000
                sh              r1,zs:$FFD10148
                ldi             r2,#10
                ldi             r6,#0
                mfspr   r5,c13
                bsr             DisplayAddr
                ldi             r2,#10
                ldi             r6,#1
                mfspr   r5,c14
                bsr             DisplayAddr
                ldi             r6,#2
                ldi             r2,#0
                ldi             r7,#0
.0001:
                ldis    60,#18          ; set breakout index to 18
                sync
                mtspr   61,r7           ; select history reg #
                sync
                ldis    60,#16          ; set breakout index to 16
                sync
                mfspr   r5,61           ; get address
                bsr             DisplayAddr
                addui   r2,r2,#1
                ldis    60,#17          ; set breakout index to 17
                sync
                mfspr   r5,61           ; get address
                bsr             DisplayAddr
                addui   r2,r2,#1
                addui   r7,r7,#1
                cmpi    p0,r7,#63
p0.ltu  br              .0001
 
brk_lockup:
                br              brk_lockup[c0]
 
; code snippet to jump to the break routine, copied to the break vector
;
; vector table jumps
;
                align   8
brk_jmp:
                jmp             brk_rout[c0]
                align   8
tms_jmp:
                jmp             tms_rout[c0]
                align   8
msi_jmp:
                jmp             msi_rout[c0]
                align   8
nmi_jmp:
                jmp             nmi_rout[c0]
                align   8
uii_jmp:
                ldi             r63,#00
                jmp             uii_rout[c0]
                align   8
vb_jmp:
                jmp             VideoBIOSCall[c0]
                align   8
ser_jmp:
                jmp             SerialIRQ[c0]
                align   8
dbe_jmp:
                jmp             dbe_rout[c0]
                align   8
svc_jmp:
                jmp             save_context[c0]
                align   8
rsc_jmp:
                jmp             restore_context[c0]
                align   8
spur_jmp:
                jmp             spur_rout[c0]
                align   8
btnu_jmp:
                jmp             btnu_rout[c0]
                align   8
rti_jmp:
km_jmp:
                rti
 
;------------------------------------------------------------------------------
; Reset Point
;------------------------------------------------------------------------------
 
                org             $FFFFEFF0
                jmp             cold_start[c15]
 
extern my_main : 24
 

Line No.	Rev	Author	Line
1	5	robfinch
2			`; ============================================================================`
3			`; __`
4			`; \\__/ o\ (C) 2015 Robert Finch, Stratford`
5			`; \ __ / All rights reserved.`
6			`; \/_// robfinch@finitron.ca`
7			`; \|\|`
8			`;`
9			`;`
10			`; This source file is free software: you can redistribute it and/or modify`
11			`; it under the terms of the GNU Lesser General Public License as published`
12			`; by the Free Software Foundation, either version 3 of the License, or`
13			`; (at your option) any later version.`
14			`;`
15			`; This source file is distributed in the hope that it will be useful,`
16			`; but WITHOUT ANY WARRANTY; without even the implied warranty of`
17			`; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the`
18			`; GNU General Public License for more details.`
19			`;`
20			`; You should have received a copy of the GNU General Public License`
21			`; along with this program. If not, see .`
22			`;`
23			`; ============================================================================`
24			`;`
25	12	robfinch
26			`SCRSZ EQU 2604`
27	5	robfinch	`CR EQU 0x0D ;ASCII equates`
28			`LF EQU 0x0A`
29			`TAB EQU 0x09`
30			`CTRLC EQU 0x03`
31			`BS EQU 0x07`
32			`CTRLH EQU 0x08`
33			`CTRLI EQU 0x09`
34			`CTRLJ EQU 0x0A`
35			`CTRLK EQU 0x0B`
36			`CTRLM EQU 0x0D`
37			`CTRLS EQU 0x13`
38			`CTRLX EQU 0x18`
39			`XON EQU 0x11`
40			`XOFF EQU 0x13`
41			`ESC EQU 0x1B`
42
43			`SC_LSHIFT EQU $12`
44			`SC_RSHIFT EQU $59`
45			`SC_KEYUP EQU $F0`
46			`SC_EXTEND EQU $E0`
47			`SC_CTRL EQU $14`
48			`SC_ALT EQU $11`
49			`SC_DEL EQU $71 ; extend`
50			`SC_LCTRL EQU $58`
51			`SC_NUMLOCK EQU $77`
52			`SC_SCROLLLOCK EQU $7E`
53			`SC_CAPSLOCK EQU $58`
54
55	12	robfinch	`E_BadFuncno EQU 1`
56			`BIOS_E_Timeout EQU 2`
57			`E_Unsupported EQU 3`
58
59			`BIOS_STACKTOP EQU $3bf8`
60			`INT_STACK EQU $37f8`
61			`VIDEO_BIOS_STACKTOP EQU $3ff8`
62
63	5	robfinch	`IOBASE_ADDR EQU 0xFFD00000`
64			`IOLMT EQU 0x100000`
65			`LEDS EQU 0xC0600`
66			`TEXTSCR EQU 0x00000`
67			`TEXTSCR2 EQU 0x10000`
68			`TEXTREG EQU 0xA0000`
69	12	robfinch	`TEXTREG2 EQU 0xA0040`
70	5	robfinch	`TEXT_COLS EQU 0x0`
71			`TEXT_ROWS EQU 0x2`
72			`TEXT_CURPOS EQU 0x16`
73			`KEYBD EQU 0xC0000`
74
75	16	robfinch	`PIC_IS EQU 0xC0FC0`
76	5	robfinch	`PIC_IE EQU 0xC0FC8`
77			`PIC_ES EQU 0xC0FE0`
78			`PIC_ESR EQU 0xC0FE8 ; edge sense reset`
79
80	16	robfinch	`bss`
81			`org $0000`
82			`dw 0 ; the first word is unused`
83			`Milliseconds dw 0`
84			`m_w dh 0`
85			`m_z dh 0`
86			`KeyState1 db 0`
87			`KeyState2 db 0`
88			`KeybdLEDs db 0`
89			`KeybdWaitFlag db 0`
90	5	robfinch
91	16	robfinch	`CursorX dc 0`
92			`CursorY dc 0`
93			`VideoPos dc 0`
94			`align 4`
95			`NormAttr dh 0`
96			`Vidregs dh 0`
97			`Vidptr dh 0`
98			`EscState dc 0`
99			`Textrows dc 0`
100			`Textcols dc 0`
101			`align 8`
102			`reg_save fill.w 64,0`
103			`creg_save fill.w 16,0`
104			`sreg_save fill.w 16,0`
105			`preg_save dw 0`
106	5	robfinch
107	12	robfinch	`bss`
108			`org $4000`
109
110
111			`rxfull EQU 1`
112			`Uart_ms db 0`
113			`Uart_txxonoff db 0`
114			`Uart_rxhead dc 0`
115			`Uart_rxtail dc 0`
116			`Uart_rxflow db 0`
117			`Uart_rxrts db 0`
118			`Uart_rxdtr db 0`
119			`Uart_rxxon db 0`
120			`Uart_foff dc 0`
121			`Uart_fon dc 0`
122			`Uart_txrts db 0`
123			`Uart_txdtr db 0`
124			`Uart_txxon db 0`
125			`Uart_rxfifo fill.b 512,0`
126
127			`NUMWKA fill.b 64,0`
128
129			`code 17 bits`
130	5	robfinch	`org $FFFF8000`
131
132			`cold_start:`
133			`; Initialize segment registers for flat model`
134			`mtspr zs,r0`
135			`ldis zs.lmt,#-1`
136			`mtspr ds,r0`
137			`ldis ds.lmt,#-1`
138			`mtspr es,r0`
139			`ldis es.lmt,#-1`
140			`mtspr fs,r0`
141			`ldis fs.lmt,#-1`
142			`mtspr gs,r0`
143			`ldis gs.lmt,#-1`
144			`ldis hs,#IOBASE_ADDR`
145			`ldis hs.lmt,#IOLMT`
146
147			`; set SS:SP`
148			`mtspr ss,r0`
149			`ldis ss.lmt,#$4000`
150	12	robfinch	`ldi r31,#$03ef8 ; initialize kernel SP`
151			`ldi r27,#$03bf8 ; initialize SP`
152	5	robfinch
153			`; switch processor to full speed`
154			`stp #$FFFF`
155
156	16	robfinch	`; set interrupt table at $1000`
157			`ldis c12,#$1000`
158	5	robfinch
159			`; set all vectors to the uninitialized interrupt vector`
160	16	robfinch	`mov r4,r0`
161			`ldis lc,#255 ; 256 vectors to set`
162			`su1:`
163			`ldi r1,#uii_jmp`
164			`mov r2,r4`
165			`bsr set_vector ; trashes r2,r3`
166			`addui r4,r4,#1`
167			`loop su1`
168	5	robfinch
169			`; setup break vector`
170	16	robfinch	`lla r1,cs:brk_jmp`
171	5	robfinch	`ldi r2,#0`
172			`bsr set_vector`
173
174	12	robfinch	`; setup Video BIOS vector`
175	16	robfinch	`lla r1,cs:vb_jmp`
176	12	robfinch	`ldi r2,#10`
177			`bsr set_vector`
178
179	5	robfinch	`; setup NMI vector`
180	16	robfinch	`lla r1,cs:nmi_jmp`
181	5	robfinch	`ldi r2,#254`
182			`bsr set_vector`
183
184	16	robfinch	`lla r1,cs:svc_jmp`
185			`ldi r2,#190`
186			`bsr set_vector`
187			`lla r1,cs:rsc_jmp`
188			`ldi r2,#191`
189			`bsr set_vector`
190
191			`; spurious interrupt`
192			`;`
193			`lla r1,cs:spur_jmp`
194			`ldi r2,#192`
195			`bsr set_vector`
196
197	12	robfinch	`; setup MSI vector`
198			`sh r0,Milliseconds`
199	16	robfinch	`lla r1,cs:msi_jmp`
200	12	robfinch	`ldi r2,#193`
201			`bsr set_vector`
202
203	5	robfinch	`; setup IRQ vector`
204	16	robfinch	`lla r1,cs:tms_jmp`
205	5	robfinch	`ldi r2,#194`
206			`bsr set_vector`
207
208	16	robfinch	`; setup BTNU vector`
209			`lla r1,cs:btnu_jmp`
210			`ldi r2,#200`
211			`bsr set_vector`
212
213			`; setup KM vector`
214			`lla r1,cs:km_jmp`
215			`ldi r2,#245`
216			`bsr set_vector`
217
218	12	robfinch	`; setup data bus error vector`
219	16	robfinch	`lla r1,cs:dbe_jmp`
220	12	robfinch	`ldi r2,#251`
221			`bsr set_vector`
222
223	5	robfinch	`; Initialize PIC`
224	16	robfinch	`ldi r1,#%00000111 ; time slice interrupt is edge sensitive`
225	5	robfinch	`sh r1,hs:PIC_ES`
226	16	robfinch	`ldi r1,#%100000111 ; enable time slice interrupt, msi, nmi`
227	5	robfinch	`sh r1,hs:PIC_IE`
228
229	16	robfinch	`; Initialize random number generator`
230			`; m_z and m_w must not be zero`
231			`ldi r1,#$88888888`
232			`sh r1,m_w`
233			`ldi r1,#$77777777`
234			`sh r1,m_z`
235
236	5	robfinch	`mov r1,r0`
237			`mov r2,r0`
238			`mov r3,r0`
239			`mov r4,r0`
240			`mov r5,r0`
241
242			`ldi r1,#1`
243	12	robfinch	`sc r1,hs:LEDS`
244	5	robfinch
245			`tlbwrreg DMA,r0 ; clear TLB miss registers`
246			`tlbwrreg IMA,r0`
247			`ldi r1,#2 ; 2 wired registers`
248			`tlbwrreg Wired,r1`
249			`ldi r1,#$2 ; 64kiB page size`
250			`tlbwrreg PageSize,r1`
251
252			`; setup the first translation`
253			`; virtual page $FFFF0000 maps to physical page $FFFF0000`
254			`; This places the BIOS ROM at $FFFFxxxx in the memory map`
255			`ldi r1,#$80000101 ; ASID=zero, G=1,valid=1`
256			`tlbwrreg ASID,r1`
257			`ldi r1,#$0FFFF`
258			`tlbwrreg VirtPage,r1`
259			`tlbwrreg PhysPage,r1`
260			`tlbwrreg Index,r0 ; select way #0`
261			`tlbwi ; write to TLB entry group #0 with hold registers`
262
263			`; setup second translation`
264			`; virtual page 0 maps to physical page 0`
265			`ldi r1,#$80000101 ; ASID=zero, G=1,valid=1`
266			`tlbwrreg ASID,r1`
267			`tlbwrreg VirtPage,r0`
268			`tlbwrreg PhysPage,r0`
269			`ldi r1,#8 ; select way#1`
270			`tlbwrreg Index,r1`
271			`tlbwi ; write to TLB entry group #0 with hold registers`
272
273			`; turn on the TLB`
274			`; tlben`
275
276			`; enable maskable interrupts`
277			`; Interrupts also are not enabled until an RTI instruction is executed.`
278			`; there will likely be a timer interrupt outstanding so this`
279			`; should go to the timer IRQ.`
280			`cli`
281
282			`; now globally enable interrupts using the RTI instruction, this will also`
283			`; switch to core to application/user mode.`
284			`ldis c14,#j1 ; c14 contains RTI return address`
285	12	robfinch	`sync`
286	16	robfinch	`rti`
287	5	robfinch	`j1:`
288			`ldi r1,#2`
289	12	robfinch	`sc r1,hs:LEDS`
290	5	robfinch	`sb r0,EscState`
291	12	robfinch	`bsr SerialInit`
292	16	robfinch	`; bsr Debugger`
293	12	robfinch	`ldi r2,#msgStartup`
294			`ldis lc,#msgStartupEnd-msgStartup-1`
295			`j3:`
296			`; lbu r1,[r2]`
297			`; addui r2,r2,#1`
298			`; tst p0,r1`
299			`;p0.eq br j2`
300			`; bsr SerialPutChar`
301			`; loop j3`
302			`j2:`
303	5	robfinch	`bsr VideoInit`
304	12	robfinch	`bsr VBClearScreen`
305			`; bsr VBClearScreen2`
306	5	robfinch	`ldi r1,#3`
307	12	robfinch	`sc r1,hs:LEDS`
308			`mov r1,r0`
309			`mov r2,r0`
310			`ldi r6,#2 ; Set Cursor Pos`
311			`sys #10`
312	5	robfinch	`ldi r1,#6`
313	12	robfinch	`sc r1,hs:LEDS`
314			`bsr alphabet`
315	16	robfinch	`lla r1,cs:msgStartup ; convert to linear address`
316	12	robfinch	`ldi r6,#$14`
317			`sys #10`
318	16	robfinch
319			`;------------------------------------------------------------------------------`
320			`;------------------------------------------------------------------------------`
321			`; Monitor`
322			`;------------------------------------------------------------------------------`
323			`;------------------------------------------------------------------------------`
324
325			`Monitor:`
326			`lla r1,cs:msgMonitor`
327			`bsr VBDisplayString`
328
329			`; Display monitor prompt`
330			`.prompt:`
331			`ldi r1,#CR`
332			`bsr VBDisplayChar`
333			`ldi r1,#LF`
334			`bsr VBDisplayChar`
335			`ldi r1,#'$'`
336			`bsr VBDisplayChar`
337			`bsr CursorOn`
338			`.getkey:`
339	5	robfinch	`bsr KeybdGetCharWait`
340	12	robfinch	`bsr VBDisplayChar`
341			`cmpi p0,r1,#CR`
342	16	robfinch	`p0.ne br .getkey`
343			`bsr CursorOff`
344			`lcu r1,CursorY`
345			`lcu r7,Textcols`
346			`mtspr lc,r7 ; use loop counter as safety`
347			`mulu r10,r1,r7 ; pos = row * cols`
348			`_4addu r10,r10,r0 ; pos *= 4`
349			`.0001:`
350			`bsr MonGetch1 ; get character skipping spaces`
351			`cmpi p0,r1,#'$' ; skip over prompt`
352			`p0.eq br .0001`
353			`cmpi p0,r1,#'d' ; debug ?`
354			`p0.eq bsr Debugger`
355			`cmpi p0,r1,#'g'`
356			`p0.eq bsr GoGraphics`
357			`cmpi p0,r1,#'t'`
358			`p0.eq bsr MonGetch`
359			`p0.eq cmpi p0,r1,#'x'`
360			`p0.eq bsr GoText`
361			`cmpi p0,r1,'r'`
362			`p0.eq bsr RandomDots`
363			`cmpi p0,r1,#'c'`
364			`p0.eq bsr VBClearScreen`
365			`p0.eq mov r1,r0`
366			`p0.eq mov r2,r0`
367			`p0.eq ldi r6,#2`
368			`p0.eq sys #10`
369			`br .prompt`
370	5	robfinch
371	16	robfinch	`;------------------------------------------------------------------------------`
372			`; Returns:`
373			`; r1 ascii code for character`
374			`; r10 incremented`
375			`; lc decremented`
376			`;------------------------------------------------------------------------------`
377
378			`MonGetch:`
379			`addui r31,r31,#-8`
380			`sws c1,[r31]`
381			`lhu r1,hs:[r10]`
382			`andi r1,r1,#$3ff`
383			`bsr VBScreenToAscii`
384			`addui r10,r10,#4`
385			`loop .0001 ; decrement loop counter`
386			`.0001:`
387			`lws c1,[r31]`
388			`addui r31,r31,#8`
389			`rts`
390
391			`;------------------------------------------------------------------------------`
392			`; Returns:`
393			`; r1 ascii code for character`
394			`; r10 incremented by number of spaces + 1`
395			`; lc decremented by number of spaces + 1`
396			`;------------------------------------------------------------------------------`
397
398			`MonGetch1:`
399			`addui r31,r31,#-8`
400			`sws c1,[r31]`
401			`.0001:`
402			`lhu r1,hs:[r10]`
403			`andi r1,r1,#$3ff`
404			`bsr VBScreenToAscii`
405			`addui r10,r10,#4`
406			`cmpi p0,r1,#' '`
407			`p0.leu loop .0001`
408			`lws c1,[r31]`
409			`addui r31,r31,#8`
410			`rts`
411
412			`;------------------------------------------------------------------------------`
413			`;------------------------------------------------------------------------------`
414
415			`GoGraphics:`
416			`lhu r3,Vidregs`
417			`ldi r1,#4`
418			`sc r1,Textrows`
419			`sh r1,hs:4[r3] ; # rows`
420			`ldi r1,#720`
421			`sh r1,hs:12[r3] ; window top`
422			`rts`
423
424			`GoText:`
425			`lhu r3,Vidregs`
426			`ldi r1,#31`
427			`sc r1,Textrows`
428			`sh r1,hs:4[r3] ; # rows`
429			`ldi r1,#17`
430			`sh r1,hs:12[r3] ; window top`
431			`rts`
432
433			`// ----------------------------------------------------------------------------`
434			`// Uses George Marsaglia's multiply method`
435			`//`
436			`// m_w = ; /* must not be zero */`
437			`// m_z = ; /* must not be zero */`
438			`//`
439			`// uint get_random()`
440			`// {`
441			`// m_z = 36969 * (m_z & 65535) + (m_z >> 16);`
442			`// m_w = 18000 * (m_w & 65535) + (m_w >> 16);`
443			`// return (m_z << 16) + m_w; /* 32-bit result */`
444			`// }`
445			`// ----------------------------------------------------------------------------`
446			`//`
447			`gen_rand:`
448			`addui r31,r31,#-8`
449			`sw r2,[r31]`
450			`lhu r1,m_z`
451			`mului r2,r1,#36969`
452			`shrui r1,r1,#16`
453			`addu r2,r2,r1`
454			`sh r2,m_z`
455
456			`lhu r1,m_w`
457			`mului r2,r1,#18000`
458			`shrui r1,r1,#16`
459			`addu r2,r2,r1`
460			`sh r2,m_w`
461			`rand:`
462			`lhu r1,m_z`
463			`shli r1,r1,#16`
464			`addu r1,r1,r2`
465			`lw r2,[r31]`
466			`addui r31,r31,#8`
467			`rts`
468
469			`// ----------------------------------------------------------------------------`
470			`// Display random dots on the graphics screen.`
471			`// ----------------------------------------------------------------------------`
472
473			`RandomDots:`
474			`addui r31,r31,#-8`
475			`sws c1,[r31]`
476			`mov r4,r0`
477			`.0001:`
478			`bsr gen_rand ; get random bitmap memory location`
479			`modu r2,r1,#172032 ; mod the memory size`
480			`shli r2,r2,#1 ; *2 for 16 bit data`
481			`bsr gen_rand ; get random color`
482			`modui r3,r1,#$1000 ; limit to 12 bits`
483			`sc r3,zs:$FFA00000[r2] ; store color in memory`
484			`addui r4,r4,#1 ; increment loop index`
485			`andi r4,r4,#$FFF ;`
486			`tst p0,r4 ; check if time to check for keypress`
487			`p0.eq bsr KeybdGetCharNoWait ; try get a key, but don't wait`
488			`tst p0,r1 ; branch if no key pressed`
489			`p0.lt br RandomDots.0001`
490			`lws c1,[r31]`
491			`addui r31,r31,#8`
492			`rts`
493
494			`;------------------------------------------------------------------------------`
495
496	5	robfinch	`msgStartup:`
497			`byte "Thor Test System Starting...",CR,LF,0`
498	12	robfinch	`msgStartupEnd:`
499	16	robfinch	`msgMonitor:`
500			`byte CR,LF`

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