further IO stack refactoring

c64/kernal/iec/ciout.s

@@ -0,0 +1,45 @@
+
+//
+// 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:
+
+#if CONFIG_IEC
+
+	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
+
+#else
+
+	sec // indicate failure
+	rts
+
+#endif

c64/kernal/iec/clrchn_iec.s

@@ -0,0 +1,30 @@
+
+//
+// IEC part of the CLRCHN routine
+//
+
+
+#if CONFIG_IEC
+
+
+clrchn_iec:
+
+	// Check input device
+	lda DFLTN
+	jsr iec_check_devnum_oc
+	bcs !+
+
+	// It was IEC device - send UNTALK first
+	jsr UNTLK
+!:
+	// Check output device
+	lda DFLTO
+	jsr iec_check_devnum_oc
+
+	// If it was IEC device - send UNLSN first
+	bcc_far UNLSN
+
+	rts
+
+
+#endif // CONFIG_IEC