mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-18 21:06:31 +00:00
132 lines
2.6 KiB
ArmAsm
132 lines
2.6 KiB
ArmAsm
; Test the 6522 on a Mockingboard running in interrupt mode
|
|
; Trying to set it to 50Hz
|
|
|
|
.include "zp.inc"
|
|
|
|
;=============================
|
|
; Print message
|
|
;=============================
|
|
jsr HOME
|
|
jsr TEXT
|
|
|
|
lda #0
|
|
sta DRAW_PAGE
|
|
sta CH
|
|
sta CV
|
|
lda #<mocking_message
|
|
sta OUTL
|
|
lda #>mocking_message
|
|
sta OUTH
|
|
jsr move_and_print
|
|
|
|
jsr mockingboard_detect_slot4
|
|
cpx #$1
|
|
beq mockingboard_found
|
|
|
|
lda #<not_message
|
|
sta OUTL
|
|
lda #>not_message
|
|
sta OUTH
|
|
inc CV
|
|
jsr move_and_print
|
|
|
|
jmp forever_loop
|
|
|
|
mockingboard_found:
|
|
lda #<found_message
|
|
sta OUTL
|
|
lda #>found_message
|
|
sta OUTH
|
|
inc CV
|
|
jsr move_and_print
|
|
|
|
;=========================
|
|
; Setup Interrupt Handler
|
|
;=========================
|
|
; Vector address goes to 0x3fe/0x3ff
|
|
; FIXME: should chain any existing handler
|
|
|
|
lda #<interrupt_handler
|
|
sta $03fe
|
|
lda #>interrupt_handler
|
|
sta $03ff
|
|
|
|
;============================
|
|
; Enable 50Hz clock on 6522
|
|
;============================
|
|
|
|
lda #$40 ; Generate continuous interrupts, don't touch PB7
|
|
sta $C40B ; ACR register
|
|
lda #$7F ; clear all interrupt flags
|
|
sta $C40E ; IER register (interrupt enable)
|
|
|
|
lda #$C0
|
|
sta $C40D ; IFR: 1100, enable interrupt on timer one oflow
|
|
sta $C40E ; IER: 1100, enable timer one interrupt
|
|
|
|
lda #$E7
|
|
sta $C404 ; write into low-order latch
|
|
lda #$4f
|
|
sta $C405 ; write into high-order latch,
|
|
; load both values into counter
|
|
; clear interrupt and start counting
|
|
|
|
; 4fe7 / 1e6 = .020s, 50Hz
|
|
|
|
;============================
|
|
; Enable 6502 interrupts
|
|
;============================
|
|
;
|
|
cli ; clear interrupt mask
|
|
|
|
|
|
;============================
|
|
; Loop forever
|
|
;============================
|
|
lda #64
|
|
forever_loop:
|
|
; clc
|
|
; adc #1
|
|
sta $0401
|
|
jmp forever_loop
|
|
|
|
|
|
|
|
;=============================
|
|
; simple interrupt handler
|
|
;=============================
|
|
; On Apple II/6502 the interrupt handler jumps to address in 0xfffe
|
|
; This is in the ROM, which saves the registers
|
|
; on older IIe it saved A to $45 (which could mess with DISK II)
|
|
; newer IIe doesn't do that.
|
|
; It then calculates if it is a BRK or not (which trashes A)
|
|
; Then it sets up the stack like an interrupt and calls 0x3fe
|
|
|
|
interrupt_handler:
|
|
pha ; save A
|
|
|
|
bit $C404 ; can clear interrupt by reading T1C-L
|
|
|
|
|
|
inc $0410 ; increment text char on screen
|
|
|
|
pla ; restore A
|
|
rti
|
|
|
|
|
|
|
|
;=========
|
|
;routines
|
|
;=========
|
|
.include "../asm_routines/gr_offsets.s"
|
|
.include "../asm_routines/text_print.s"
|
|
.include "../asm_routines/mockingboard.s"
|
|
|
|
;=========
|
|
; strings
|
|
;=========
|
|
mocking_message: .asciiz "LOOKING FOR MOCKINGBOARD IN SLOT #4"
|
|
not_message: .byte "NOT "
|
|
found_message: .asciiz "FOUND"
|
|
done_message: .asciiz "DONE PLAYING"
|