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.nolist

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.include "m168def.inc"      ; Same family as 328P

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.list

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.macro poke

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		.message	"No parameters"

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.endm

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.macro poke_i_8_i

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		ldi			@1, @2

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		sts			@0, @1

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.endm

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.macro poke_i_16_i

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		ldi			@1, low(@3)

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		sts			@0+0, @1

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		ldi			@2, high(@3)

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		sts			@0+1, @2

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.endm

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;; Load a 16-bit *word* address into the given register a a byte address

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.macro loadp_16_i

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		ldi			@0, high(2 * @2)

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		ldi			@1, low(2 * @2)

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.endm

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.macro load_16_i

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		ldi			@0, high(@2)

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		ldi			@1, low(@2)

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.endm

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;; Interrupt Vector

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        rjmp        Main

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;; Serial

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.set SERIAL_BAUD = 103		; 9.6k @ 16Mhz

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;; Initialize the UART for 

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Serial_Init:

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	; Set up control registers

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		; Single-speed

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		poke		[UCSR0A, r16, (0 << U2X0)]

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		; Async

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		; n parity

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		; 1 stop

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		; 8 bits

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		poke		[UCSR0C, r16, (0b00 << UMSEL00) | (0b00 << UPM00) | (0 << USBS0) | (0b11 << UCSZ00)]

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		; Baud rate

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		poke		[UBRR0L, r16:r17, SERIAL_BAUD]

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		; Enable RX

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		; Enable TX

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		; 8 bits

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		poke		[UCSR0B, r16, (1 << RXEN0) | (1 << TXEN0) | (0 << UCSZ02)]

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	; Done

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		ret

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;; Send a single byte on serial port

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; Input byte in r16

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Serial_Send:

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	; Wait for idle

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		lds			r0, UCSR0A

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		sbrs		r0, UDRE0

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		rjmp		Serial_Send

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	; Copy byte to buffer

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		sts			UDR0, r16

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	; Done

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		ret

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;; Read a single byte from serial port

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; Output byte in r16

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Serial_Recv:

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	; Wait for recv

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		lds			r0, UCSR0A

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		sbrs		r0, RXC0

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		rjmp		Serial_Recv

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	; Copy byte from buffer

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		lds			r16, UDR0

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	; Done

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		ret

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;; Write nul-terminated string to serial port

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; Input string in Z

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	; Load byte to r16

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		lpm			r16, Z+

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	; Quit if nul

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		tst			r16

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	; Write it

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		rcall		Serial_Send

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	; Continue

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		ret

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;; Program

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message:	.db "Hello World", 13, 10, 0

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Main:

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; Initialization

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	; Stack

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		poke		[SPL, r16:r17, RAMEND]

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    ; Enable interrupts

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        sei

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	; Init

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		rcall		Serial_Init

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; Main program

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		ldi			ZH, high(message * 2)

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		ldi			ZL, low(message * 2)

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; Echo out

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		sbi			DDRB, PORTB5

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		ldi			r20, 0

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Main_Echo:

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		out			PORTB, r20

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		rcall		Serial_Recv

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		rcall		Serial_Send

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		com			r20

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		rjmp		Main_Echo

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