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; Copyright (c)2022 Jeremy Seth Henry

; All rights reserved.

;

; Redistribution and use in source and binary forms, with or without

; modification, are permitted provided that the following conditions are met:

;     * Redistributions of source code must retain the above copyright

;       notice, this list of conditions and the following disclaimer.

;     * Redistributions in binary form must reproduce the above copyright

;       notice, this list of conditions and the following disclaimer in the

;       documentation and/or other materials provided with the distribution,

;       where applicable (as part of a user interface, debugging port, etc.)

;

; THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY

; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

; DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY

; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

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; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

;

;------------------------------------------------------------------------------

; taskmgr_const.s

;

;  Task Manager constants, tables, and macros

;

; Revision History

; Author          Date     Change

;---------------- -------- ----------------------------------------------------

; Seth Henry      7/15/22  Initial Release

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Semaphore Value - should always be non-zero

.DEFINE SEMAPHORE_VAL        $FF       ; Standard value used to set semaphores

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; I/O Mapping (HDL -> ASSY)

;------------------------------------------------------------------------------

; System RAM Write-Protect Register

.DEFINE WPR_MASK_REG         WPR_Address

; Write Protect Mask

.DEFINE WPR_MASK_0           WPR_MASK_REG + 0

.DEFINE WPR_MASK_1           WPR_MASK_REG + 1

.DEFINE WPR_MASK_2           WPR_MASK_REG + 2

.DEFINE WPR_MASK_3           WPR_MASK_REG + 3

; WP Register Map:

; Offset  Bitfield Description                        Read/Write

;   0x00  AAAAAAAA Region Enables  7:0                  (RW)

;   0x01  AAAAAAAA Region Enables 15:8                  (RW)

;   0x02  AAAAAAAA Region Enables 23:16                 (RW)

;   0x03  AAAAAAAA Region Enables 31:24                 (RW)

; I/O Write Qualification Register

.DEFINE IO_WRITE_QUAL        WQL_Address

; External Interrupt Manager / Task Timer

.DEFINE INT_MGR_IF           INT_Address ; Shared with the main

.DEFINE TASK_TIMER_PRD       INT_MGR_IF  + 0

; Defines for the 8-bit interrupt manager

.DEFINE EXT_INT_MASK         INT_MGR_IF + 1

.DEFINE EXT_INT_PEND         INT_MGR_IF + 2

.DEFINE EXT_INT_ACK          INT_MGR_IF + 3

; Defines for the 16-bit interrupt manager

.DEFINE EXT_INT16_MASK_L     INT_MGR_IF + 2

.DEFINE EXT_INT16_MASK_H     INT_MGR_IF + 3

.DEFINE EXT_INT16_PEND_L     INT_MGR_IF + 4

.DEFINE EXT_INT16_PEND_H     INT_MGR_IF + 5

.DEFINE EXT_INT16_ACK        INT_MGR_IF + 7

; Register Map:

; Offset  Bitfield Description                        Read/Write

;   0x00  AAAAAAAA PIT Timer Interval (0 = disabled)    (RW)

;   0x01  AAAAAAAA External Interrupt Mask              (RW)

;   0x02  AAAAAAAA Pending External Ints*               (RW)

;   0x02  A------- Interrupt Requested (write to clear) (RW)

; External Interrupt bit & mask definitions

.DEFINE EXT_INT0_BIT         2^0

.DEFINE EXT_INT1_BIT         2^1

.DEFINE EXT_INT2_BIT         2^2

.DEFINE EXT_INT3_BIT         2^3

.DEFINE EXT_INT4_BIT         2^4

.DEFINE EXT_INT5_BIT         2^5

.DEFINE EXT_INT6_BIT         2^6

.DEFINE EXT_INT7_BIT         2^7

.DEFINE EXT_INT8_BIT         2^0

.DEFINE EXT_INT9_BIT         2^1

.DEFINE EXT_INT10_BIT        2^2

.DEFINE EXT_INT11_BIT        2^3

.DEFINE EXT_INT12_BIT        2^4

.DEFINE EXT_INT13_BIT        2^5

.DEFINE EXT_INT14_BIT        2^6

.DEFINE EXT_INT15_BIT        2^7

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Register the interrupt service routines and form the vector address table at

;  the end of the ROM

;------------------------------------------------------------------------------

.ORG ISR_Start_Addr

.DW RAM_FAULT        ; (0xFFF1:0xFFF0) ISR 0

.DW TASK_SW_INT      ; (0xFFF3:0xFFF2) ISR 1

.DW EXT_INT_MGR      ; (0xFFF5:0xFFF4) ISR 2

.DW EXEC_SUPV0       ; (0xFFF7:0xFFF6) ISR 3

.DW EXEC_SUPV1       ; (0xFFF9:0xFFF8) ISR 4

.DW EXEC_SUPV2       ; (0xFFFB:0xFFFA) ISR 5

.DW EXEC_SUPV3       ; (0xFFFD:0xFFFC) ISR 6

.DW EXEC_SUPV4       ; (0xFFFF:0xFFFE) ISR 7

.DEFINE CPU_INT_ENABLES      $FF

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Pointer Defines and Table Organization

;------------------------------------------------------------------------------

; Create defined constants to pointer table

; Note that these are offset by 4 to account for the bootstrap JMP and NOP

.DEFINE STACK_MEMORY_PTR     BOOT_BLOCK +  4

.DEFINE FREE_SYSMEM_PTR      BOOT_BLOCK +  6

.DEFINE TASK_PARAMS_PTR      BOOT_BLOCK +  8

.DEFINE TASK_PARAM_TABLE     BOOT_BLOCK +  10

.MACRO INSTANCE_TASK_POINTERS

.DW TaskMgr.Task_Stacks   ; ( + 4) First available RAM location for stack data

.DW TaskMgr.Free_Mem      ; ( + 6) First available free RAM location in sysmem

.DW TASK_PARAM_TABLE      ; ( + 8) Start of task parameter table

.ENDM

;------------------------------------------------------------------------------

; INSTANCE_TASK_EXPORTS / CREATE_TASK_EXPORTS setup a ROM table for the task

;  switcher with critical entry points and memory & I/O write access

;  permissions. The entry points are created automatically by

;  INSTANCE_MAIN_LOOPS, while the other constants are setup in taskmgr_config.s

;  based on its task configuration and memory needs

;------------------------------------------------------------------------------

.DEFINE STACK_TABLE_OFFSET    2

.DEFINE PARAM_TABLE_OFFSET   20

; Define table offsets to allow quick use of LDO to access individual records

;  for each task

.DEFINE PARAM_MAIN_ADDR_LOW   0

.DEFINE PARAM_MAIN_ADDR_HIGH  1

.DEFINE PARAM_STACK_ADDR_LOW  2

.DEFINE PARAM_STACK_ADDR_HIGH 3

.DEFINE PARAM_WPR_BYTE0       4

.DEFINE PARAM_WPR_BYTE1       5

.DEFINE PARAM_WPR_BYTE2       6

.DEFINE PARAM_WPR_BYTE3       7

.DEFINE PARAM_WQL_LOW         8

.DEFINE PARAM_WQL_HIGH        9

.DEFINE SUPV_FN0_ENTRY_LOW    10

.DEFINE SUPV_FN0_ENTRY_HIGH   11

.DEFINE SUPV_FN1_ENTRY_LOW    12

.DEFINE SUPV_FN1_ENTRY_HIGH   13

.DEFINE SUPV_FN2_ENTRY_LOW    14

.DEFINE SUPV_FN2_ENTRY_HIGH   15

.DEFINE SUPV_FN3_ENTRY_LOW    16

.DEFINE SUPV_FN3_ENTRY_HIGH   17

.DEFINE SUPV_FN4_ENTRY_LOW    18

.DEFINE SUPV_FN4_ENTRY_HIGH   19

; CREATE_TASK_EXPORTS creates an entry in the TASK_PARAM_TABLE with critical

;  task information. Note that the WPR_LOW, WPR_HIGH, and WQL must be defined

;  in taskmgr_config.s. Everything else is automatically created here, or by

;  the assembler/linker.

.MACRO CREATE_TASK_EXPORTS

.DEFINE TASK\@_STACK_END      RAM_Address + (TASK\@_STACK_RGN * WP_Rgn_Size)

.DEFINE TASK\@_STACK_START    TASK\@_STACK_END + WP_Rgn_Size - 1

.DW TASK\@_MAIN          ; 1:0 Entry point created by INSTANCE_MAIN_LOOPS

.DW TASK\@_STACK_START   ; 3:2 Pointer to top of the task stack

.DW TASK\@_WPR_LOW       ; 5:4 Mask for enabling task mem writes for vars

.DW TASK\@_WPR_HIGH      ; 7:6 Mask for enabling task mem writes for stack

.DW TASK\@_WQL           ; 9:8 Mask for enabling task I/O write access

.DW _F0_EXE_S\@          ; 11:10 Entry point for supervisory function 0

.DW _F1_EXE_S\@          ; 13:12 Entry point for supervisory function 1

.DW _F2_EXE_S\@          ; 15:14 Entry point for supervisory function 2

.DW _F3_EXE_S\@          ; 17:16 Entry point for supervisory function 3

.DW _F4_EXE_S\@          ; 19:18 Entry point for supervisory function 4

.ENDM

.MACRO INSTANCE_TASK_EXPORTS

    .REPEAT TASK_COUNT

        CREATE_TASK_EXPORTS

    .ENDR

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

;  Memory Structures and Variable Organization

;------------------------------------------------------------------------------

; Variable    Size      Description

; --------    ----      -------------------------------------------------------

.STRUCT str_task_label

Label         DW        ; 2-byte "header" to allow task RAM to be easily found

.ENDST

.STRUCT str_isr_flag

Flag          DB        ; Single-byte flag variable for returning semaphores

.ENDST

.DEFINE TSB_SIZE             2 * TASK_COUNT

.DEFINE FREE_SYS             WP_Rgn_Size - 8 - TSB_SIZE

.STRUCT str_taskman

This_Task     DB           ; Holds the task number of the current task

Next_Task     DB           ; Specifieds which task to be executed next

Fault_Flag    DB           ; Memory write fault flag

Fault_Task    DB           ; Task active/responsible for write fault

Temp_R0       DB           ; Temp storage for R0

Temp_R1       DB           ; Temp storage for R1

Temp_R2       DB           ; Temp storage for R2

Temp_R3       DB           ; Temp storage for R3

Task_Stacks   DSB TSB_SIZE ; First location for stack data*

Free_Mem      DSB FREE_SYS ; Unused memory in system region

.ENDST

; * Note that this location is used to setup a pointer, which the task manager

;  will use to assign each task a backup location for its current stack pointer

;  Thus, this area grows up to 2x the number tasks. The type is intentionally

;  set as DB as a reminder. If attempting to reuse memory in this region, this

;  should be noted

.ENUM SYSTEM_VARMEM

TaskMgr       INSTANCEOF str_taskman

.ENDE

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Utility macros for booting the system and providing access to internal vars

;------------------------------------------------------------------------------

; The Open8 supports an optional mode for the RSP instruction that

;  converts it from Reset Stack Pointer to Relocate Stack Pointer.

; The new form of the instruction takes one of the CPU flags as a

;  direction/mode bit. Setting PSR_S will cause the instruction

;  to write R1:R0 -> SP, while clearing it will cause the instruction

;  to copy the SP -> R1:R0.

.MACRO RETRIEVE_SP

              CLP  PSR_S   ; Affirmatively clear PSR_S flag first

              RSP          ; Then execute the RSP instruction

.ENDM

.MACRO RELOCATE_SP

              STP  PSR_S   ; Affirmatively set PSR_S flag first

              RSP          ; Execute the RSP instruction

              CLP  PSR_S   ; Reset PSR_GP4 afterward

.ENDM

; Task initialization, switching time, and init/exec macros

.MACRO DISABLE_PREEMPTION_TIMER

              CLR  R0                     ; Make sure the PIT is disabled

              STA  R0, TASK_TIMER_PRD     ; by writing 0 to the PIT period

.ENDM

.MACRO RESET_PREEMPTION_TIMER

              LDI  R0, #MAX_TASK_TIMESLICE; Turn on the PIT timer at this point

              STA  R0, TASK_TIMER_PRD     ;  to kick off the task switcher

.ENDM

; Fault flag macros

.MACRO INITIALIZE_FAULT_FLAGS

              CLR  R0

              STA  R0, TaskMgr.Fault_Flag

              STA  R0, TaskMgr.Fault_Task

.ENDM

.MACRO SET_FAULT_FLAGS

              LDI  R0, #SEMAPHORE_VAL

              STA  R0, TaskMgr.Fault_Flag

              LDA  R0, TaskMgr.This_Task

              STA  R0, TaskMgr.Fault_Task;

.ENDM

; TASK_SETUP is a template used to generate code that sets up a single task's

; stack and stack pointer for each a task. This macros will temporarily

;  relocate the stack pointer, push the task's initial state to the task's

;  stack. Note that it is important to also ensure that the stack has data to

;  not only restore the return address, but also R7:R0, as well as the flag

;  state.

.MACRO TASK_SETUP

              ; Setup a pointer in R3:R2 to the beginning of the parameter

              ;  table to load task information from.

              LDI  R0, #\@

              LDI  R1, #PARAM_TABLE_OFFSET

              MUL  R1

              LDA  R2, TASK_PARAMS_PTR + 0  ; Load R3:R2 with the start of the

              LDA  R3, TASK_PARAMS_PTR + 1  ;  task paramenter region

              ADD  R2

              T0X  R2

              TX0  R1

              ADC  R3

              T0X  R3

              ; Get the task's starting stack address from the table and load

              ;  it into the CPU SP

              LDO  R2, PARAM_STACK_ADDR_HIGH

              T0X  R1

              LDO  R2, PARAM_STACK_ADDR_LOW

              RELOCATE_SP                 ; R1:R0 -> CPU SP

              ; From here on out, the CPU SP is pointing to the target task's

              ;  stack region, so we can initialize its stack memory

              ; Write initial flag value

              CLR  R0

              PSH  R0

              ; Initialize the return address to point to the "initialize"

              ;  portion of the task, so that the task can do its one-time

              ;  startup code.

              LDO  R2, PARAM_MAIN_ADDR_HIGH ; Write return PC MSB

              PSH  R0

              LDO  R2, PARAM_MAIN_ADDR_LOW  ; Write return PC LSB

              PSH  R0

              ; Setup the initial reg values

              CLR  R0                  ; Initialize all registers to 0

              PSH  R0                  ; R0

              PSH  R0                  ; R1

              PSH  R0                  ; R2

              PSH  R0                  ; R3

              PSH  R0                  ; R4

              PSH  R0                  ; R5

              PSH  R0                  ; R6

              PSH  R0                  ; R7

              ; Once the task's stack has been initialized, retrieve the new

              ;  stack pointer from the SP and store it in the task's backup

              ;  variable.

              LDI  R0, #\@

              LDI  R1, #STACK_TABLE_OFFSET

              MUL  R1

              LDA  R2, STACK_MEMORY_PTR + 0

              LDA  R3, STACK_MEMORY_PTR + 1

              ADD  R2

              T0X  R2

              TX0  R1

              ADC  R3

              T0X  R3

              RETRIEVE_SP

              STX  R2

              TX0  R1

              STO  R2,1

.ENDM

; INSTANCE_TASK_SETUP expands to create setup code for all of the tasks based

;  on the template above. There should be one setup per task, hence the repeat

;  based on TASK_COUNT

.MACRO INSTANCE_TASK_SETUP

          .REPT TASK_COUNT

              TASK_SETUP

          .ENDR

.ENDM

; REINIT_STACK_BUFFER_PTR uses the This_Task variable to configure R3:R2 as a

;  pointer into the system memory where stack pointer backups are stored.

.MACRO REINIT_STACK_BUFFER_PTR

              LDA  R0, TaskMgr.This_Task    ; Get the task number

              LDI  R1, #STACK_TABLE_OFFSET  ; Multiply it by 2

              MUL  R1

              LDA  R2, STACK_MEMORY_PTR + 0 ; Load R3:R2 with the start of the

              LDA  R3, STACK_MEMORY_PTR + 1 ;  stack memory region

              ADD  R2                  ; Add [R3:R2] + [R1:R0] -> [R3:R2]

              T0X  R2

              TX0  R1

              ADC  R3

              T0X  R3

.ENDM

; REINIT_TASK_TABLE_PTR uses the This_Task variable to configure R3:R2 as a

;  pointer into the TASK_PARAMS table.

.MACRO REINIT_TASK_TABLE_PTR

              LDA  R0, TaskMgr.This_Task

              LDI  R1, #PARAM_TABLE_OFFSET

              MUL  R1

              LDA  R2, TASK_PARAMS_PTR + 0  ; Load R3:R2 with the start of the

              LDA  R3, TASK_PARAMS_PTR + 1  ;  task parameter region

              ADD  R2                       ; Add [R3:R2] + [R1:R0] -> [R3:R2]

              T0X  R2

              TX0  R1

              ADC  R3

              T0X  R3

.ENDM

; BACKUP_FULL_CONTEXT pushes all 8 registers to the stack

.MACRO BACKUP_FULL_CONTEXT

              PSH  R0

              PSH  R1

              PSH  R2

              PSH  R3

              PSH  R4

              PSH  R5

              PSH  R6

              PSH  R7

.ENDM

; RESTORE_FULL_CONTEXT pops all 8 registers off of the stack

.MACRO RESTORE_FULL_CONTEXT

              POP  R7

              POP  R6

              POP  R5

              POP  R4

              POP  R3

              POP  R2

              POP  R1

              POP  R0

.ENDM

; SUSPEND_CURRENT_TASK pushes all of the registers to a task's stack, then

;  backups up the stack pointer to the system memory backup location for that

;  task.

.MACRO SUSPEND_CURRENT_TASK

              BACKUP_FULL_CONTEXT

              REINIT_STACK_BUFFER_PTR

              RETRIEVE_SP              ; Copy CPU SP -> R1:R0

              STX  R2                  ; Push R1:R0 -> [R3:R2]*

              TX0  R1

              STO  R2,1

.ENDM

; AWAKEN_NEXT_TASK is responsible for updating the Next_Task variable, then

;  using it to restore the stack pointer from the system memory copy. It then

;  updates the memory write protection parameters and I/O write qualification

;  register for the new task. Finally, it resets the pre-emption timer and

;  restores the register state from the task's stack.

.MACRO AWAKEN_NEXT_TASK

              LDA  R1, TaskMgr.Next_Task ; Copy Next_Task -> This_Task

              STA  R1, TaskMgr.This_Task

; This is a simple round-robin scheduler, unless an ISR alters the Next_Task

;  variable, so increment the task count, check it against the total task

;  count, and reset it to task 0 if necessary.

              INC  R1                  ; Increment the task count

              LDI  R0, #TASK_COUNT     ; Compare it with the task count

              XOR  R1

              BNZ _TS_ADV_TN_\@        ; If it matches the task count

              LDI  R1, #$00            ;  reset the counter to zero

_TS_ADV_TN_\@:STA  R1, TaskMgr.Next_Task ; Store the new value into Next_Task

              REINIT_STACK_BUFFER_PTR  ; Lookup the new task's table pointer

              LDO  R2, PARAM_MAIN_ADDR_HIGH ; Push [R3:R2]* -> R1:R0

              T0X  R1

              LDO  R2, PARAM_MAIN_ADDR_LOW

              RELOCATE_SP              ; Update R1:R0 -> CPU SP

              REINIT_TASK_TABLE_PTR    ; Setup R3:R2 to point to the task table

              ; Rewrite the RAM WPR register for this task. Note that the WPR

              ; is a 32-bit register.

              LDO  R2, PARAM_WPR_BYTE0

              STA  R0, WPR_MASK_0

              LDO  R2, PARAM_WPR_BYTE1

              STA  R0, WPR_MASK_1

              LDO  R2, PARAM_WPR_BYTE2

              STA  R0, WPR_MASK_2

              LDO  R2, PARAM_WPR_BYTE3

              STA  R0, WPR_MASK_3

              LDO  R2, PARAM_WQL_LOW   ; Update the new task's WQL

              STA  R0, IO_WRITE_QUAL

              RESET_PREEMPTION_TIMER   ; Reset the PIT timer

              RESTORE_FULL_CONTEXT     ; Restore the new task's register state

              RTI

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; System Start

;

; System initialization requires that the CPU start in supervisor mode, as it

;  writes to every active region in memory. Thus, if the CPU is NOT in

;  in supervisor mode, something has gone horribly wrong. This branch locks the

;  main loop if the I bit is not set. This is probably unnecessary now that the

;  panic ISR is in place.

;------------------------------------------------------------------------------

; INIT_NEXT_TASK forces the Next_Task variable to 0 (Task 0)

.MACRO INIT_NEXT_TASK

              CLR  R0

              STA  R0, TaskMgr.Next_Task

.ENDM

.MACRO BOOT_SYSTEM

; Before beginning, turn off all of the CPU interrupts (The NMI will still be

;  active, but memory write protection is effectively disabled with the I-bit

;  set) Note that this code is running in interrupt context (I-bit is set)

;  so it is "uninterruptible" due to the HDL generic being set. However, this

;  doesn't prevent pending interrupts from being latched by the CPU.

; Note that this macro is defined in "isr_const.s"

              DISABLE_CPU_INTS

; Even though interrupts are off, disable the task timer so that there isn't

;  a pending task timer interrupt waiting when interrupts are re-enabled. This

;  avoids the first task missing out on initialization.

              DISABLE_PREEMPTION_TIMER

; Initialize the system fault flags

              INITIALIZE_FAULT_FLAGS

; Setup the stack and stack pointer for each of the tasks. (see above)

              INSTANCE_TASK_SETUP

; Before starting, make sure the external interrupt controller has been

;  initialized. Initialization of the external interrupt controller involves

;  clearing any pending interrupts and setting up the interrupt mask. Finally,

;  the CPU interrupts should be enabled at this point, as the interrupt core is

;  ready.

.IFDEF INTMGR16

              INITIALIZE_IO_INTMGR16      ; Setup the 16-bit IF

.ELSE

              INITIALIZE_IO_INTMGR        ; Setup the 8-bit IF

.ENDIF

; Once the external interrupt manager is configured, enable the CPU interrupts

              ENABLE_CPU_INTS             ; Enable the CPU interrupt inputs

; Like the task switcher ISR, restore the full CPU state for the first task

              INIT_NEXT_TASK

              AWAKEN_NEXT_TASK

; Create all of the task loops here.

              INSTANCE_TASK_LOOPS

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Task Loops

;------------------------------------------------------------------------------

; INSTANCE_MAIN_LOOP:

; These loops represent each task's "main()", and should never "exit".

; Each task's func.s file should declare two required functions, TASKn_INIT and

; TASKn_EXEC

;

; Note that the call to the task switch ISR occurs prior to the task's exec

;  function to allow every task to finish its setup BEFORE any task begins

;  processing.

;

; Last, the final branch is only taken if the I bit is still NOT set. If it

;  somehow gets set, the task will trigger a system panic (which never returns)

; There should be one loop per task. Note that the labels are used in to create

;  the table of entry points

.MACRO INSTANCE_TASK_LOOP

TASK\@_MAIN:  JSR  TASK\@_INIT

_TASK\@_LOOP: CALL_TASK_SW

              JSR  TASK\@_EXEC

              BNI  _TASK\@_LOOP

              CALL_PANIC

.ENDM

; INSTANCE_MAIN_LOOPS expands to create the stub main loops for all of the

;  tasks based on the template above. There should be one setup per task, hence

;  the repeat based on TASK_COUNT. Note that the output labels will be used to

;  populate fields in the task parameter table.

.MACRO INSTANCE_TASK_LOOPS

              .REPEAT TASK_COUNT

              INSTANCE_TASK_LOOP

              .ENDR

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Software-callable Interrupts

;------------------------------------------------------------------------------

; CALL_PANIC executes the same ISR as a memory fault and triggers the shutdown

;  sequence. This requires a hard-reset to recover

.MACRO CALL_PANIC

              INT  0

.ENDM

; CALL_TASK_SW executes the same ISR as the pre-emption timer, and allows tasks

;  to give up any remaining time

.MACRO CALL_TASK_SW

              INT  1

.ENDM

; Interrupt 2 is reserved for the external interrupt manager. Calling it would

;  likely be harmless, but do no real work.

; CALL_SUPV_FNn allow tasks to execute code in an interrupt/supervisor context

;  and should be used with caution.

.MACRO CALL_SUPV_FN0

              INT  3

.ENDM

.MACRO CALL_SUPV_FN1

              INT  4

.ENDM

.MACRO CALL_SUPV_FN2

              INT  5

.ENDM

.MACRO CALL_SUPV_FN3

              INT  6

.ENDM

.MACRO CALL_SUPV_FN4

              INT  7

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

;  CPU Interrupt Control Macros

;------------------------------------------------------------------------------

.MACRO DISABLE_CPU_INTS

              CLR  R0

              SMSK

.ENDM

.MACRO ENABLE_CPU_INTS

              LDI  R0, #CPU_INT_ENABLES

              SMSK

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; RAM Access Fault Shutdown (CALL_PANIC)

;  If a task manages to cause a memory fault, sets default conditions and

;   then soft-halts the CPU.

;  Note that DISABLE_PREEMPTION_TIMER, SET_FAULT_FLAGS are defined in

;   "main_const.s", while PANIC_HALT macro calls each task's PANICn_HALT macro

;------------------------------------------------------------------------------

.MACRO PROCESS_RAM_FAULT

              DISABLE_CPU_INTS         ; Disable interrupts

              DISABLE_PREEMPTION_TIMER ; Disable the task timer

              SET_FAULT_FLAGS          ; Copy the faulting task info

              EXEC_PANIC_HALT          ; Run any necessary shutdown code

_RFLT_HALT:   WAI                      ; Soft-Halt the CPU

              JMP  _RFLT_HALT          ; This shouldn't happen, but if it does

.ENDM

.MACRO CREATE_PANIC_TASK_BLOCK

              LDI  R0, #\@

              LDI  R1, #PARAM_TABLE_OFFSET

              MUL  R1

              LDA  R2, TASK_PARAMS_PTR + 0  ; Load R3:R2 with the start of the

              LDA  R3, TASK_PARAMS_PTR + 1  ;  task parameter region

              ADD  R2                  ; Add [R3:R2] + [R1:R0] -> [R3:R2]

              T0X  R2

              TX0  R1

              ADC  R3

              T0X  R3

              ; Update the WQL for the task's panic code so each task isn't

              ;  doing this on its own

              LDO  R2, PARAM_WQL_LOW

              STA  R0, IO_WRITE_QUAL

              TASK\@_PANIC

.ENDM

.MACRO EXEC_PANIC_HALT

              .REPEAT TASK_COUNT

              CREATE_PANIC_TASK_BLOCK

              .ENDR

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; Task Switcher ISR (CALL_TASK_SW)

;

; Handles switching context between tasks when called.

;------------------------------------------------------------------------------

.MACRO SWITCH_TASKS

              SUSPEND_CURRENT_TASK

              AWAKEN_NEXT_TASK

.ENDM

;------------------------------------------------------------------------------

;------------------------------------------------------------------------------

; External System Interrupt Map & ISR Macros

; This code configures the external I/O interrupt manager at startup

;------------------------------------------------------------------------------

; Setup the external I/O Interrupt manager by writing the mask registers and

;  clearing any pending interrupts. Note that the interrupt enable constants

;  are defined in ext_isr_config.s

.MACRO INITIALIZE_IO_INTMGR

              CLR  R0                     ; Disable all external interrupts

              STA  R0, EXT_INT_MASK

              LDI  R0, #SEMAPHORE_VAL     ; Clear any pending interrupts

              STA  R0, EXT_INT_PEND       ;  and do a master acknowledge

              STA  R0, EXT_INT_ACK

              LDI  R0, #EXT_INTERRUPT_EN_L; Re-enable the external interrupts

              STA  R0, EXT_INT_MASK

.ENDM

.MACRO INITIALIZE_IO_INTMGR16

              CLR  R0                     ; Disable all external interrupts

              STA  R0, EXT_INT16_MASK_L

              STA  R0, EXT_INT16_MASK_H

              LDI  R0, #SEMAPHORE_VAL     ; Clear any pending interrupts

              STA  R0, EXT_INT16_PEND_L   ;  and do a master acknowledge

              STA  R0, EXT_INT16_PEND_H

              STA  R0, EXT_INT16_ACK

              LDI  R0, #EXT_INTERRUPT_EN_L; Re-enable the external interrupts

              STA  R0, EXT_INT16_MASK_L

              LDI  R0, #EXT_INTERRUPT_EN_H; Re-enable the external interrupts

              STA  R0, EXT_INT16_MASK_H

.ENDM

; Sets up an individual external interrupt macro. Note that these refer to

;  macros defined in ext_isr_config.s

.MACRO PROCESS_EXT_ISR

              SET_INT\@_FLAGS

              TX0  R3                  ; When done with the flags, update the

              LDI  R1, #EXT_INT\@_BIT  ;  mask clear register with the ext bit

              OR   R1                  ;  and restore it to R3. Then, before

              T0X  R3                  ;  falling into the next check, make

              TX0  R2                  ;  sure to restore the current ints

.ENDM

; This code checks the external I/O interrupt manager status and processes the

;  flag code for each interrupt source.

.MACRO CHECK_EXTERNAL_IO_INTS

_EXT_INT_STRT:PSH  R0

              PSH  R1

              PSH  R2

              PSH  R3

_EXT_INT_LO:  CLR  R0                  ; R3 will be our pending mask clear reg,

              T0X  R3                  ;  so clear it here

              LDA  R0, EXT_INT_PEND    ; R2 will be our current pending reg, so

              T0X  R2                  ;  load it from the hardware here

_EXT_INT_0:   BTT  0

              BRZ  _EXT_INT_1

              PROCESS_EXT_ISR

_EXT_INT_1:   BTT  1

              BRZ  _EXT_INT_2

              PROCESS_EXT_ISR

_EXT_INT_2:   BTT  2

              BRZ  _EXT_INT_3

              PROCESS_EXT_ISR