111 lines
2.2 KiB
ArmAsm
111 lines
2.2 KiB
ArmAsm
; Function defined on pp272-273 of C64 Programmers Reference Guide
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;; See also http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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;; XXX rework this, according to pagetable.com
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open:
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;; LAT / FAT / SAT support implemented according to
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;; 'Compute's Mapping the Commodore 64', page 52
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;; Check if we have space in tables
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ldy LDTND
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cpy #$0A
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bcs +
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bmi open_has_space
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*
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;; Table is full - according to https://codebase64.org/doku.php?id=base:kernalreference
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;; C flag set means error occured
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sec
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rts
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open_has_space:
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;; Update the tables
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lda current_logical_filenum
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sta LAT, y
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lda current_device_number
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sta FAT, y
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lda current_secondary_address
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sta SAT, y
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iny
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sty LDTND
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;; Kernal API is shared between several types of devices - we have
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;; to dispatch the call to appropriate subroutine
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lda current_device_number
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beq open_keyboard
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cmp #$01
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beq open_tape
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cmp #$02
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beq open_rs232
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cmp #$03
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beq open_screen
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cmp #$1F
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bcs +
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bmi open_iec
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*
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;; Device numbers over 30 are not allowed on IEC bus
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;; FALLTHROUGH to error routine
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open_keyboard:
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open_tape:
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open_screen:
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;; XXX implement support for these devices
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lda #$05 ; device not present
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sta IOSTATUS
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rts
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open_rs232:
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;; XXX implement support for RS-232
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lda #$FF ; set every single error bit to discourage using RS-232
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sta RSSTAT
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rts
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open_iec:
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;; Part implemented according to https://www.pagetable.com/?p=1031, https://github.com/mist64/cbmbus_doc
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;; XXX note: this is only a temporary test implementation, real 'open' does not send anything to IEC,
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;; see http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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;; Disable IRQs, since timing matters!
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sei
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;; Begin sending under attention
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;; XXX jsr iec_assert_atn
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;; Request device to talk
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lda current_device_number
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jsr talk
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bcs open_iec_error
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;; Send secondary address
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lda current_secondary_address
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jsr second
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bcs open_iec_error
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;; Turnaround
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jsr iec_turnaround_to_listen
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bcs open_iec_error
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jsr printf
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.byte "DBG: TURNAROUND SUCCEEDED", $0D, 0
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;; Indicate success
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lda #$00
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clc
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open_iec_error:
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;; Re-enable interrupts and return
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;; (iec_tx_byte will have set/cleared C flag and put result code
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;; in A if it was an error).
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cli
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rts
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