Added serial test

debug/Makefile

@@ -1,4 +1,4 @@
-all: timer_test.bin basic_test.bin
+all: timer_test.bin basic_test.bin serial_test.bin
 
 %.bin: %.o
 	m68k-elf-ld --oformat binary -Ttext=0x0 -o $@ $<

debug/serial_test.s

@@ -0,0 +1,68 @@
+/*
+	Serial port is located at 15MB + 3*64KB = 0xF30000
+	Note that since the port is connected to 8 bits of a 16 bit bus,
+	The offsets for each serial register have to be doubled.
+*/
+	.equ SPORT_LOC, 0xF30000
+	.global _start
+
+	.long 0x12500				/* stack ptr */
+	.long _start
+
+	.org 0x400
+_start:
+	/* disable interrupts */
+	ORI.W #0x700, %sr
+	/* Setup serial */
+	JSR init_serial
+	/* Send hello world */
+	MOVE.L HELLO_WORLD, %a0
+	JSR serial_send_string
+	/* Echo chars forever */
+ECHO_LOOP:
+	JSR serial_rx_char
+	JSR serial_send_char
+	JMP ECHO_LOOP
+
+init_serial:
+	MOVE.B #0b00000011, (SPORT_LOC) /* Channel A mode reg 1 */
+	MOVE.B #0b00000111, (SPORT_LOC) /* Channel A mode reg 2 */
+	MOVE.B #0b10111011, (SPORT_LOC + 2) /* 9600 baud */
+	MOVE.B #0b01100000, (SPORT_LOC + 8) /* ACR */
+	MOVE.B #0b00000101, (SPORT_LOC + 4) /* CRA, enable serial A */
+	RTS
+
+	# char goes in d0
+serial_send_char:
+	MOVE.B (SPORT_LOC + 2), %d1	/* SRA */
+	AND #0b00000100, %d1		/* TXRDY */
+	CMP #0, %d1
+	BEQ serial_send_char		/* wait for TXRDY */
+	MOVE.B %d0, (SPORT_LOC + 6) /* send char */
+	RTS
+
+	# a0 - pointer to string
+serial_send_string:
+	MOVE.B (%a0), %d0			/* load cur char */
+	CMP #0, %d0					/* check if NULL */
+	BEQ serial_send_string_done
+	JSR serial_send_char		/* print char */
+	ADD.L #1, %a0				/* inc ptr */
+	JMP serial_send_string		/* loop */
+	
+serial_send_string_done:
+	RTS
+
+	/* char placed in d0 */
+serial_rx_char:
+	MOVE.B (SPORT_LOC + 2), %d1 /* SRA */
+	AND.B #1, %d1
+	CMP.B #0, %d1					/* wait for RXRDY */
+	BEQ serial_rx_char
+	MOVE.B (SPORT_LOC + 6), %d0
+	RTS
+	
+
+HELLO_WORLD:
+	.ascii "Hello World!"
+	.byte 0