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[/] [socgen/] [trunk/] [Projects/] [opencores.org/] [Mos6502/] [sw/] [boot_basic/] [boot_basic.asm] - Blame information for rev 133

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; minimal monitor for EhBASIC and 6502 simulator V1.05
 
; To run EhBASIC on the simulator load and assemble [F7] this file, start the simulator
; running [F6] then start the code with the RESET [CTRL][SHIFT]R. Just selecting RUN
; will do nothing, you'll still have to do a reset to run the code.
 
        .include "basic.asm"
 
; put the IRQ and MNI code in RAM so that it can be changed
 
IRQ_vec = VEC_SV+2              ; IRQ code vector
NMI_vec = IRQ_vec+$0A   ; NMI code vector
 
; setup for the 6502 simulator environment
 
IO_AREA = $F000         ; set I/O area for this monitor
 
ACIAsimwr       = IO_AREA+$01   ; simulated ACIA write port
ACIAsimrd       = IO_AREA+$04   ; simulated ACIA read port
 
; now the code. all this does is set up the vectors and interrupt code
; and wait for the user to select [C]old or [W]arm start. nothing else
; fits in less than 128 bytes
 
        *=      $FF80                   ; pretend this is in a 1/8K ROM
 
; reset vector points here
 
RES_vec
        CLD                             ; clear decimal mode
        LDX     #$FF                    ; empty stack
        TXS                             ; set the stack
 
; set up vectors and interrupt code, copy them to page 2
 
        LDY     #END_CODE-LAB_vec       ; set index/count
LAB_stlp
        LDA     LAB_vec-1,Y             ; get byte from interrupt code
        STA     VEC_IN-1,Y              ; save to RAM
        DEY                             ; decrement index/count
        BNE     LAB_stlp                ; loop if more to do
 
; now do the signon message, Y = $00 here
 
LAB_signon
        LDA     LAB_mess,Y              ; get byte from sign on message
        BEQ     LAB_nokey               ; exit loop if done
 
        JSR     V_OUTP          ; output character
        INY                             ; increment index
        BNE     LAB_signon              ; loop, branch always
 
LAB_nokey
        JSR     V_INPT          ; call scan input device
        BCC     LAB_nokey               ; loop if no key
 
        AND     #$DF                    ; mask xx0x xxxx, ensure upper case
        CMP     #'W'                    ; compare with [W]arm start
        BEQ     LAB_dowarm              ; branch if [W]arm start
 
        CMP     #'C'                    ; compare with [C]old start
        BNE     RES_vec         ; loop if not [C]old start
 
        JMP     LAB_COLD                ; do EhBASIC cold start
 
LAB_dowarm
        JMP     LAB_WARM                ; do EhBASIC warm start
 
; byte out to simulated ACIA
 
ACIAout
        STA     ACIAsimwr               ; save byte to simulated ACIA
        RTS
 
; byte in from simulated ACIA
 
ACIAin
        LDA     ACIAsimrd               ; get byte from simulated ACIA
        BEQ     LAB_nobyw               ; branch if no byte waiting
 
        SEC                             ; flag byte received
        RTS
 
LAB_nobyw
        CLC                             ; flag no byte received
no_load                         ; empty load vector for EhBASIC
no_save                         ; empty save vector for EhBASIC
        RTS
 
; vector tables
 
LAB_vec
        .word   ACIAin          ; byte in from simulated ACIA
        .word   ACIAout         ; byte out to simulated ACIA
        .word   no_load         ; null load vector for EhBASIC
        .word   no_save         ; null save vector for EhBASIC
 
; EhBASIC IRQ support
 
IRQ_CODE
        PHA                             ; save A
        LDA     IrqBase         ; get the IRQ flag byte
        LSR                             ; shift the set b7 to b6, and on down ...
        ORA     IrqBase         ; OR the original back in
        STA     IrqBase         ; save the new IRQ flag byte
        PLA                             ; restore A
        RTI
 
; EhBASIC NMI support
 
NMI_CODE
        PHA                             ; save A
        LDA     NmiBase         ; get the NMI flag byte
        LSR                             ; shift the set b7 to b6, and on down ...
        ORA     NmiBase         ; OR the original back in
        STA     NmiBase         ; save the new NMI flag byte
        PLA                             ; restore A
        RTI
 
END_CODE
 
LAB_mess
        .byte   $0D,$0A,"6502 EhBASIC [C]old/[W]arm ?",$00
                                        ; sign on string
 
; system vectors
 
        *=      $FFFA
 
        .word   NMI_vec         ; NMI vector
        .word   RES_vec         ; RESET vector
        .word   IRQ_vec         ; IRQ vector
 

Line No.	Rev	Author	Line
1	131	jt_eaton
2			`; minimal monitor for EhBASIC and 6502 simulator V1.05`
3
4			`; To run EhBASIC on the simulator load and assemble [F7] this file, start the simulator`
5			`; running [F6] then start the code with the RESET [CTRL][SHIFT]R. Just selecting RUN`
6			`; will do nothing, you'll still have to do a reset to run the code.`
7
8			`.include "basic.asm"`
9
10			`; put the IRQ and MNI code in RAM so that it can be changed`
11
12			`IRQ_vec = VEC_SV+2 ; IRQ code vector`
13			`NMI_vec = IRQ_vec+$0A ; NMI code vector`
14
15			`; setup for the 6502 simulator environment`
16
17			`IO_AREA = $F000 ; set I/O area for this monitor`
18
19			`ACIAsimwr = IO_AREA+$01 ; simulated ACIA write port`
20			`ACIAsimrd = IO_AREA+$04 ; simulated ACIA read port`
21
22			`; now the code. all this does is set up the vectors and interrupt code`
23			`; and wait for the user to select [C]old or [W]arm start. nothing else`
24			`; fits in less than 128 bytes`
25
26			`*= $FF80 ; pretend this is in a 1/8K ROM`
27
28			`; reset vector points here`
29
30			`RES_vec`
31			`CLD ; clear decimal mode`
32			`LDX #$FF ; empty stack`
33			`TXS ; set the stack`
34
35			`; set up vectors and interrupt code, copy them to page 2`
36
37			`LDY #END_CODE-LAB_vec ; set index/count`
38			`LAB_stlp`
39			`LDA LAB_vec-1,Y ; get byte from interrupt code`
40			`STA VEC_IN-1,Y ; save to RAM`
41			`DEY ; decrement index/count`
42			`BNE LAB_stlp ; loop if more to do`
43
44			`; now do the signon message, Y = $00 here`
45
46			`LAB_signon`
47			`LDA LAB_mess,Y ; get byte from sign on message`
48			`BEQ LAB_nokey ; exit loop if done`
49
50			`JSR V_OUTP ; output character`
51			`INY ; increment index`
52			`BNE LAB_signon ; loop, branch always`
53
54			`LAB_nokey`
55			`JSR V_INPT ; call scan input device`
56			`BCC LAB_nokey ; loop if no key`
57
58			`AND #$DF ; mask xx0x xxxx, ensure upper case`
59			`CMP #'W' ; compare with [W]arm start`
60			`BEQ LAB_dowarm ; branch if [W]arm start`
61
62			`CMP #'C' ; compare with [C]old start`
63			`BNE RES_vec ; loop if not [C]old start`
64
65			`JMP LAB_COLD ; do EhBASIC cold start`
66
67			`LAB_dowarm`
68			`JMP LAB_WARM ; do EhBASIC warm start`
69
70			`; byte out to simulated ACIA`
71
72			`ACIAout`
73			`STA ACIAsimwr ; save byte to simulated ACIA`
74			`RTS`
75
76			`; byte in from simulated ACIA`
77
78			`ACIAin`
79			`LDA ACIAsimrd ; get byte from simulated ACIA`
80			`BEQ LAB_nobyw ; branch if no byte waiting`
81
82			`SEC ; flag byte received`
83			`RTS`
84
85			`LAB_nobyw`
86			`CLC ; flag no byte received`
87			`no_load ; empty load vector for EhBASIC`
88			`no_save ; empty save vector for EhBASIC`
89			`RTS`
90
91			`; vector tables`
92
93			`LAB_vec`
94			`.word ACIAin ; byte in from simulated ACIA`
95			`.word ACIAout ; byte out to simulated ACIA`
96			`.word no_load ; null load vector for EhBASIC`
97			`.word no_save ; null save vector for EhBASIC`
98
99			`; EhBASIC IRQ support`
100
101			`IRQ_CODE`
102			`PHA ; save A`
103			`LDA IrqBase ; get the IRQ flag byte`
104			`LSR ; shift the set b7 to b6, and on down ...`
105			`ORA IrqBase ; OR the original back in`
106			`STA IrqBase ; save the new IRQ flag byte`
107			`PLA ; restore A`
108			`RTI`
109
110			`; EhBASIC NMI support`
111
112			`NMI_CODE`
113			`PHA ; save A`
114			`LDA NmiBase ; get the NMI flag byte`
115			`LSR ; shift the set b7 to b6, and on down ...`
116			`ORA NmiBase ; OR the original back in`
117			`STA NmiBase ; save the new NMI flag byte`
118			`PLA ; restore A`
119			`RTI`
120
121			`END_CODE`
122
123			`LAB_mess`
124			`.byte $0D,$0A,"6502 EhBASIC [C]old/[W]arm ?",$00`
125			`; sign on string`
126
127			`; system vectors`
128
129			`*= $FFFA`
130
131			`.word NMI_vec ; NMI vector`
132			`.word RES_vec ; RESET vector`
133			`.word IRQ_vec ; IRQ vector`
134

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[/] [socgen/] [trunk/] [Projects/] [opencores.org/] [Mos6502/] [sw/] [boot_basic/] [boot_basic.asm] - Blame information for rev 133