125 lines
3.6 KiB
ArmAsm
125 lines
3.6 KiB
ArmAsm
;;; The Cricket Clock - ProDOS Patcher
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;;; Disassembled from /CRICKET/PRODOS.MOD
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;;; Original: Street Electronics Corporation (C) 1984
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.setcpu "6502"
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.include "apple2.inc"
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.include "opcodes.inc"
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.include "../../inc/apple2.inc"
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.include "../../inc/prodos.inc"
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.org $300
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.proc install
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ptr := $42
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;; Copy driver to target in ProDOS
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lda DATETIME+1
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sta ptr
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lda DATETIME+2
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sta ptr+1
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lda #OPC_JMP_abs ; JMP opcode
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sta DATETIME
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lda ROMIN ; Write bank 2
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lda ROMIN
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ldy #sizeof_driver-1
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loop: lda driver,y
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sta (ptr),y
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dey
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bpl loop
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;; Simple exit when BRUN
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rts
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.endproc
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;; Driver - relocatable code. Called by ProDOS to update date/time bytes
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.proc driver
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scratch := $3A ; ZP scratch location
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;; Initialize
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php
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sei
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lda COMMAND ; save status of command register
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pha
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;; Configure SSC
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lda #%00001011 ; no parity/echo/interrupts, RTS low, DTR low
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sta COMMAND
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lda #%10011110 ; 9600 baud, 8 data bits, 2 stop bits
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sta CONTROL
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;; Send command
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: lda STATUS
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and #(1 << 4) ; transmit register empty? (bit 4)
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beq :- ; nope, keep waiting
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lda #('@' | $80) ; '@' command
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sta TDREG
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read_len := 7 ; read 7 bytes (w/m/d/y/H/M/S)
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;; Read response, pushing to stack
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ldy #(read_len-1)
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rloop: ldx #0 ; x = retry loop counter low byte
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lda #3 ; scratch = retry loop counter high byte
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sta scratch ; ($300 iterations total)
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check: lda STATUS ; did we get it?
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and #(1 << 3) ; receive register full? (bit 3)
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bne ready ; yes, we read the value
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inx ; not yet, so keep trying
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bne check ; until counter runs out
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dec scratch
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bne check
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;; Read failed - restore stack and exit
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reset: cpy #(read_len-1) ; anything left to restore?
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beq done ; nope, exit
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pla ; yep, clear it off the stack
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iny
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bne reset
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;; Read succeeded - stuff it on the stack and continue
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ready: lda RDREG
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pha
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dey
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bpl rloop
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;; Convert pushed response to ProDOS time field
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pla ; day of week (unused)
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pla ; minute
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sta TIMELO ; -- stored as-is (TIMELO 5-0)
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pla ; hour
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sta TIMELO+1 ; -- stored as-is (TIMELO 12-8)
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pla ; year
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sta DATELO+1 ; -- will be shifted up by 1 (DATELO 15-9)
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pla ; day
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and #%00011111 ; -- masked, stored as is (DATELO 4-0)
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sta DATELO
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pla ; month
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asl a ; -- shifted up (DATELO 8-5)
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asl a
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asl a
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asl a
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asl a
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ora DATELO ; -- merge low 5 bits
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sta DATELO
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rol DATELO+1
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pla ; seconds (unused)
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;; Restore prior state
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done: pla ; restore saved command state
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sta COMMAND
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plp
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rts
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.endproc
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sizeof_driver := .sizeof(driver)
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