52 lines
1.0 KiB
ArmAsm
52 lines
1.0 KiB
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 301/302
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// - [CM64] Compute's Mapping the Commodore 64 - page 223
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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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TALK:
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#if CONFIG_IEC
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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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// Check whether device number is correct
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jsr iec_check_devnum_oc
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bcc !+
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jmp kernalerror_DEVICE_NOT_FOUND
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!:
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// Encode and execute the command
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ora #$40
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// FALLTROUGH
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common_talk_listen: // common part of TALK and LISTEN
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sta TBTCNT
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#if CONFIG_IEC_JIFFYDOS
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// It seems that only TALK/LISTEN is used to detect the JiffyDOS support
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lda #$FF // unknown protocol - check what is supported
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sta IECPROTO
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#endif // CONFIG_IEC_JIFFYDOS
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jmp iec_tx_command
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#else
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jmp kernalerror_ILLEGAL_DEVICE_NUMBER
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#endif
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