various I/O updates

c64/kernal/rs232/open_rs232.s

@@ -7,9 +7,40 @@
 #if HAS_RS232
 
 
+#if CONFIG_MEMORY_MODEL_60K
+	.error "CONFIG_MEMORY_MODEL_60K is not compatible with RS-232 memory allocation code"
+#endif
+
+
 open_rs232:
-	
-	// XXX provide implementation for both UP2400 and UP9600
+
+	// First check how many RS-232 channels are currently allocated.
+	// If more than one, skip allocation (already allocated).
+
+	jsr rs232_count_channels
+	bcs open_rs232_end
+
+	// Allocate buffer
+
+	lda MEMSIZK+0
+	sta ROBUF+0
+	sta RIBUF+0
+
+	dec MEMSIZK+1
+	lda MEMSIZK+1
+	sta ROBUF+1	  // XXX RIBUF or ROBUF?
+
+	dec MEMSIZK+1
+	lda MEMSIZK+1
+	sta RIBUF+1	  // XXX RIBUF or ROBUF?
+
+	lda #$00
+	sta RIDBE
+	sta RIDBS
+	sta RODBS
+	sta RODBE
+
+open_rs232_end:
 
 	jmp open_done_success