//
// Official Kernal routine, described in:
//
// - [RG64] C64 Programmer's Reference Guide   - page 279/280
// - [CM64] Compute's Mapping the Commodore 64 - page 224
//
// CPU registers that has to be preserved (see [RG64]): .X, .Y
//


CIOUT:

	pha
	lda C3PO
	bne ciout_send_byte

	// Nothing to send - set buffer as valid, store byte there
	inc C3PO

	// Clear carry flag to indicate success
	clc
	
ciout_store_in_buffer:

	// Store in the buffer data to be sent next, return
	pla
	sta BSOUR
	rts
	
ciout_send_byte:

	clc // don't send with EOI
	jsr iec_tx_byte
	inc C3PO // iec_tx_byte sets it to 0, but we still have something to send
	jmp ciout_store_in_buffer