53 lines
937 B
ArmAsm
53 lines
937 B
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# * KERNAL_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Official Kernal routine, described in:
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//
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// - [RG64] C64 Programmers Reference Guide - page 279/280
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// - [CM64] Computes Mapping the Commodore 64 - page 224
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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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CIOUT:
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#if CONFIG_IEC
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pha
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lda C3PO
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bne ciout_send_byte
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// Nothing to send - set buffer as valid, store byte there
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inc C3PO
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// Clear carry flag to indicate success
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clc
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ciout_store_in_buffer:
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// Store in the buffer data to be sent next, return
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pla
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sta BSOUR
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rts
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ciout_send_byte:
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clc // send without EOI
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#if CONFIG_IEC_JIFFYDOS
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jsr iec_tx_dispatch
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#else
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jsr iec_tx_byte
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#endif
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inc C3PO // tx byte routine sets to 0, but we still have something to send
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jmp ciout_store_in_buffer
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#else
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sec // indicate failure
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rts
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#endif
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