43 lines
895 B
ArmAsm
43 lines
895 B
ArmAsm
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;;
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;; Kernal internal IEC routine
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;;
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;; - https://www.pagetable.com/?p=1031, https://github.com/mist64/cbmbus_doc
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;;
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iec_cmd_open: ; similar to TKSA, but without turnaround
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jsr iec_check_channel_openclose
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bcc +
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jmp kernalerror_FILE_NOT_INPUT
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*
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ora #$F0
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;; FALLTROUGH
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common_open_close_unlsn_second: ; common part of several commands
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sta IEC_TMP2
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jsr iec_tx_command
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bcs + ; branch if error
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jmp iec_tx_command_finalize
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*
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rts
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iec_check_channel_openclose:
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;; Due to OPEN/CLOSE/TKSA/SECOND command encoding (see https://www.pagetable.com/?p=1031),
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;; allowed channels are 0-15; report error if out of range
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cmp #$10
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bcc +
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;; Workaround to allow reading executable files and disk directory
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;; using OPEN routine - see https://www.pagetable.com/?p=273 for
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;; example usage
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cmp #$60
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beq +
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sec ; mark unsuitable channel number
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rts
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*
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clc ; mark suitable channel number
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rts
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