//
// Kernal internal IEC routine
//
// - https://www.pagetable.com/?p=1031, https://github.com/mist64/cbmbus_doc
//


#if CONFIG_IEC


iec_cmd_open: // similar to TKSA, but without turnaround

	jsr iec_check_channel_openclose
	bcc !+
	jmp kernalerror_FILE_NOT_INPUT
!:
	ora #$F0

	// FALLTROUGH

common_open_close_unlsn_second: // common part of several commands

	sta TBTCNT
	jsr iec_tx_command
	bcs !+ // branch if error
	jmp iec_tx_command_finalize
!:
	rts

iec_check_channel_openclose:
	// Due to OPEN/CLOSE/TKSA/SECOND command encoding (see https://www.pagetable.com/?p=1031),
	// allowed channels are 0-15; report error if out of range
	cmp #$10
	bcc !+ 
	// Workaround to allow reading executable files and disk directory
	// using OPEN routine - see https://www.pagetable.com/?p=273 for
	// example usage
	cmp #$60
	beq !+
	sec // mark unsuitable channel number
	rts
!:
	clc // mark suitable channel number
	rts


#endif // CONFIG_IEC