Kernal size optimizations

c64/kernal/status.s

@@ -0,0 +1,42 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+
+// Kernal status codes are described in 'Commodore 64 Programmers Reference Guide', page 292
+
+kernalstatus_reset:
+	lda #$00
+	beq kernalstatus_end               // branch always
+
+// The following two statuses are currently not implemented - and most likely not really needed
+
+// kernalstatus_TIMEOUT_WRITE:
+//
+//	lda IOSTATUS
+//	ora #K_STS_TIMEOUT_WRITE
+//	bne kernalstatus_end               // branch always
+
+// kernalstatus_TIMEOUT_READ:
+//
+//	lda IOSTATUS
+//	ora #K_STS_TIMEOUT_READ
+//	bne kernalstatus_end               // branch always
+
+kernalstatus_EOI:
+
+	lda IOSTATUS
+	ora #K_STS_EOI
+	bne kernalstatus_end               // branch always
+
+kernalstatus_DEVICE_NOT_FOUND:
+
+	lda IOSTATUS
+	ora #K_STS_DEVICE_NOT_FOUND
+
+	// FALLTROUGH
+
+kernalstatus_end:
+
+	sta IOSTATUS
+	rts