16 lines
437 B
ArmAsm
16 lines
437 B
ArmAsm
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iec_pull_data_release_atn_clk:
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;; Released CLK = DATA considered valid; for extra robustness on non-emulated
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;; hardware give some lines few more cycles to stabilize; see page 10 of
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;; http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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lda CI2PRA
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ora #BIT_CI2PRA_DAT_OUT ; pull
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sta CI2PRA
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and #$FF - BIT_CI2PRA_CLK_OUT ; release
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sta CI2PRA
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and #$FF - BIT_CI2PRA_ATN_OUT ; release
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sta CI2PRA
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rts
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