385 lines
13 KiB
ArmAsm
385 lines
13 KiB
ArmAsm
; Fully disassembled and analyzed source to AE
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; DCLOCK.SYSTEM by M.G. - 04/18/2017
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; https://gist.github.com/mgcaret/7f0d7aeec169e90809c7cfaab9bf183b
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; Further modified by @inexorabletash - 12/21/2020
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; There are critical bugs in the original AE code:
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; * When driver loader is initially probing it corrupts the
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; Apple //c Memory Expansion Card:
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; - it saves, but fails to restore, data at address $080000
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; - it fails to reset slinky pointer, and *will* trash $080000-$080007
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; * When the clock is read, it corrupts data at address $08xx01
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; - John Brooks spotted this, [M.G.] totally missed this.
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; This version of the code has fixes permanently applied.
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.setcpu "65C02"
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.linecont +
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.feature string_escapes
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.include "apple2.inc"
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.include "apple2.mac"
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.include "opcodes.inc"
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.include "../../inc/apple2.inc"
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.include "../../inc/macros.inc"
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.include "../../inc/prodos.inc"
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; zero page locations
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SCRATCH := $0B ; scratch value for BCD range checks
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SAVEBYTE := $0C ; slinky overwritten byte save location
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BCDTMP := $3A ; location clock driver uses for BCD->Binary
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; buffers & other spaces
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INBUF := $0200 ; input buffer
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CLOCKBUF := $0300 ; clock buffer
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; I/O and hardware
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C8OFF := $CFFF ; C8xx ROM off
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SLOT4ROM := $C400 ; Slot 4 ROM space
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SLOT4IO := $C0C0 ; Slot 4 I/O space
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DPTRL := SLOT4IO+0 ; Slinky data ptr low
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DPTRM := SLOT4IO+1 ; Slinky data ptr middle
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DPTRH := SLOT4IO+2 ; Slinky data ptr high
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DATA := SLOT4IO+3 ; Slinky data byte
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;;; ************************************************************
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.include "../../inc/driver_preamble.inc"
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;;; ************************************************************
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;;; ============================================================
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;;;
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;;; Driver Installer
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;;;
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;;; ============================================================
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.define PRODUCT "DClock"
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;;; ============================================================
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;;; Ensure there is not a previous clock driver installed.
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;;; And that this is a IIc. And that the clock is present.
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.proc maybe_install_driver
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lda MACHID
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and #$01 ; existing clock card?
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bne done
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lda VERSION ; IIc identification byte 1
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cmp #$06
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bne done
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lda ZIDBYTE ; IIc identification byte 2
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cmp #$00
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bne done
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jsr ClockRead
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jsr ValidTime
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bcc InstallDriver
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;; Show failure message
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jsr log_message
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scrcode PRODUCT, " - Not Found."
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.byte 0
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done: rts
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.endproc
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; ----------------------------------------------------------------------------
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; Install clock driver
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.proc InstallDriver
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;; Copy into address at DATETIME vector, update the vector and
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;; update MACHID bits to signal a clock is present.
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ptr := $A5
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;; Update absolute addresses within driver
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lda DATETIME+1
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sta ptr
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clc
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adc #(regulk - driver)
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sta regulk_addr
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lda DATETIME+2
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sta ptr+1
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adc #0
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sta regulk_addr+1
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;; Copy driver into appropriate bank
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lda RWRAM1
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lda RWRAM1
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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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;; Set the "Recognizable Clock Card" bit
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lda MACHID
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ora #$01
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sta MACHID
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lda #OPC_JMP_abs
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sta DATETIME
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;; Invoke the driver to init the time
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jsr DATETIME
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lda ROMIN2
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;; Display success message
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jsr log_message
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scrcode PRODUCT, " - "
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.byte 0
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;; Display the current date
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jsr cout_date
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rts ; done!
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.endproc
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; ----------------------------------------------------------------------------
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; enable slinky registers, set adddress and save byte we intend to trash
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.proc SlinkyEnable
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lda C8OFF ; not needed on //c, but release $C8xx firmware
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lda SLOT4ROM ; enable slinky registers
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lda #$08 ; set addr $080000
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sta DPTRH
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stz DPTRM
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stz DPTRL
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lda DATA ; read data byte
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sta SAVEBYTE ; save it to restore later
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; Routine to restore trashed byte in slinky RAM
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.proc SlinkyRestore
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lda #$08 ; set adddr $080000
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sta DPTRH
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stz DPTRM
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stz DPTRL
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lda SAVEBYTE ; get saved byte
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sta DATA ; and put it back
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lda C8OFF ; not needed on //c, but release $C8xx firmware
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; Write 8 bits to clock
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.proc ClockWrite8b
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ldx #$08 ; set adddr $080000
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stx DPTRH
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stz DPTRM
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: stz DPTRL ; restore low byte to 0
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sta DATA ; write byte
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lsr a ; next bit into 0 position
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dex
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bne :-
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; unlock the clock by writing the magic bit sequence
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.proc ClockUnlock
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ldy #$08
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: lda unlock,y
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jsr ClockWrite8b ; write 8 bits
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dey
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bne :-
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rts
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unlock = * - 1
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.byte $5c, $a3, $3a, $c5, $5c, $a3, $3a, $c5
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.endproc
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; ----------------------------------------------------------------------------
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; Read 8 bits from the clock
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.proc ClockRead8b
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ldx #$08 ; set adddr $080000
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stz DPTRL
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stz DPTRM
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stx DPTRH
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: pha ; save accumulator
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lda DATA ; get data byte
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lsr a ; bit 0 into carry
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pla ; restore accumulator
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ror a ; put read bit into position
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dex
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bne :-
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; read the clock data into memory at CLOCKBUF
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; WARNING: unfixed code never restores byte we trashed
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.proc ClockRead
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jsr SlinkyEnable
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jsr ClockUnlock
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ldy #$00
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: jsr ClockRead8b
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sta CLOCKBUF,y
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iny
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cpy #$08 ; have we read 8 bytes?
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bcc :- ; nope
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jsr SlinkyRestore
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; validate the DClock data makes sense
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; return carry clear if it does, carry set if it does not
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.proc ValidTime
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; validate ms
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ldx #$00
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ldy #$99
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lda CLOCKBUF
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jsr CheckBCD
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bcs :+
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; validate seconds
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ldx #$00
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ldy #$59
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lda CLOCKBUF+$01
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jsr CheckBCD
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bcs :+
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; validate minutes
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ldx #$00
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ldy #$59
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lda CLOCKBUF+$02
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jsr CheckBCD
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bcs :+
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; validate hours
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ldx #$00
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ldy #$23
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lda CLOCKBUF+$03
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jsr CheckBCD
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bcs :+
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; validate day of week
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ldx #$01
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ldy #$07
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lda CLOCKBUF+$04
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jsr CheckBCD
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bcs :+
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; validate day of month
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ldx #$01
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ldy #$31
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lda CLOCKBUF+$05
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jsr CheckBCD
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bcs :+
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; validate month
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ldx #$01
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ldy #$12
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lda CLOCKBUF+$06
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jsr CheckBCD
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bcs :+
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; validate year
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ldx #$00
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ldy #$99
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lda CLOCKBUF+$07
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jsr CheckBCD
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bcs :+
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clc ; all good
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rts
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: sec ; problem
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; Check BCD number in range of [x,y]
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; return carry clear if it is, carry set if it is not
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.proc CheckBCD
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sed ; decimal mode
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stx SCRATCH ; lower bound into scratch
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cmp SCRATCH ; compare it
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bcc :++ ; fail if out of range
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sty SCRATCH ; upper bound into scratch
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cmp SCRATCH ; compare it
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beq :+ ; OK if equal
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bcs :++ ; fail if out of range
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: cld ; in range
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clc
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rts
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: cld ; not in range
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sec
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rts
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.endproc
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; ----------------------------------------------------------------------------
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; clock driver code inserted into ProDOS
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driver:
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lda #$08 ; useless instruction
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php
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sei
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lda SLOT4ROM ; activate slinky registers
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; ($08 from above overwritten)
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stz DPTRL ; set slinky address to $08xx00
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ldy #$08 ; also counter for unlock bytes
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sty DPTRH
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lda DATA ; get destroyed byte
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; (slinky now at $08xx01)
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pha ; save value on stack
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; unlock dclock registers
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regulk_addr := *+1
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ubytlp: lda regulk,y ; self-modified
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ldx #$08 ; bit counter
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ubitlp: stz DPTRL ; reset pointer to $08xx00
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sta DATA ; write to $08xx00
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lsr a ; next bit into 0 position
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dex
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bne ubitlp
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dey
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bne ubytlp
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; now read 64 bits (8 bytes) from dclock
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ldx #$08 ; byte counter
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rbytlp: ldy #$08 ; bit counter
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rbitlp: pha
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lda DATA ; data byte
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lsr a ; bit 0 into carry
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pla
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ror a ; carry into bit 7
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dey
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bne rbitlp
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; got 8 bits now, convert from BCD to binary
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pha
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and #$0F
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sta BCDTMP
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pla
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and #$F0
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lsr a
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pha
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adc BCDTMP
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sta BCDTMP
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pla
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lsr a
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lsr a
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adc BCDTMP
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; place in input buffer, which is OK because the ThunderClock driver does this
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sta INBUF-1,x
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dex
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bne rbytlp
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; done copying, now put necessary values into ProDOS time locations
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; copy hours to ProDOS hours
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lda INBUF+4
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sta TIMEHI
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; copy minutes to ProDOS minutes
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lda INBUF+5
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sta TIMELO
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; copy month ...
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lda INBUF+1
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lsr a
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ror a
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ror a
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ror a
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; ... and day of month to ProDOS month/day
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ora INBUF+2
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sta DATELO
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; copy year and final bit of month to ProDOS year/month
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lda INBUF
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rol a
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sta DATEHI
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stz DPTRL ; set slinky back to $08xx00
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pla ; get saved byte
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sta DATA ; put it back
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plp
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rts
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; DS1215 unlock sequence (in reverse)
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regulk = * - 1
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.byte $5C, $A3, $3A, $C5, $5C, $A3, $3A, $C5
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sizeof_driver := * - driver
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.assert sizeof_driver <= 125, error, "Clock code must be <= 125 bytes"
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;;; ************************************************************
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.include "../../inc/driver_postamble.inc"
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;;; ************************************************************
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