26 lines
580 B
ArmAsm
26 lines
580 B
ArmAsm
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;;
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;; Official Kernal routine, described in:
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;;
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;; - [RG64] C64 Programmer's Reference Guide - page 303
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;; - [CM64] Compute's Mapping the Commodore 64 - page 224
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;; - https://www.pagetable.com/?p=1031, , https://github.com/mist64/cbmbus_doc
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;; - http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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;;
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;; CPU registers that has to be preserved (see [RG64]): .X, .Y
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;;
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unlsn:
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;; According to serial-bus.pdf (page 15) this routine flushes the IEC out buffer
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jsr iec_tx_flush
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;; Buffer empty, send the command
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lda #$3F
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jmp common_open_close_unlsn_second
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