[avrcpm.git] / avr / sw-uart.asm

; Serial interface using the ATmega8/88 USART. 
; This is part of the Z80-CP/M emulator written by Sprite_tm.
;
;    Copyright (C) 2010 Leo C.
;
;    This file is part of avrcpm.
;
;    avrcpm is free software: you can redistribute it and/or modify it
;    under the terms of the GNU General Public License as published by
;    the Free Software Foundation, either version 3 of the License, or
;    (at your option) any later version.
;
;    avrcpm is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;    GNU General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with avrcpm.  If not, see <http://www.gnu.org/licenses/>.
;
;    $Id$
;

#define SSER_BIT_TC	(F_CPU+BAUD/2) / BAUD 

#define RXBUFMASK  	RXBUFSIZE-1
#define TXBUFMASK  	TXBUFSIZE-1

	.dseg
	
srx_state:
	.byte	1
srx_char_to:
	.byte	1
srx_dr:
	.byte	1
;srx_lastedge:
;	.byte	2
stx_bitcount:
	.byte	1
stx_dr:
	.byte	1
rxcount:
	.byte	1
rxidx_w:
	.byte	1
rxidx_r:
	.byte	1
txcount:
	.byte	1
txidx_w:
	.byte	1
txidx_r:
	.byte	1
rxfifo:
	.byte	RXBUFSIZE
txfifo:
	.byte	TXBUFSIZE


	.cseg

; Init 
uart_init:

; - Init clock/timer system and serial port

; Init timer 1 as 
; - Soft UART TX (OC1A/OCR1A).
; - Soft UART RX (ICP1/ICR1).
; - 1ms System timer is already configured at this point.

	ldi	temp,(1<<COM1A1)|(1<<COM1A0)	;OC1A high on compare match (UART TX)
	outm8	TCCR1A,temp

	ldi	temp,(1<<ICF1)			;clear pending int
	out	TIFR1,temp
	inm8	temp,TIMSK1
	ori	temp,(1<<ICIE1)			;Enable input capture int.  (UART RX)
	outm8	TIMSK1,temp
	ret
	
;------------------------------------------------------------------

	.cseg

; Timer/Counter1 Input Capture interrupt
	
	INTERRUPT ICP1addr
	
	push	temp
	in	temp,sreg
	push	temp
	push	zh
	push	zl
	inm8	zl,ICR1L
	inm8	zh,ICR1H
	push	temp2
	ldi	temp2,(1<<ICES1)
	inm8	temp,TCCR1B
	eor	temp,temp2			;toggle edge
	outm8	TCCR1B,temp
	ldi	temp,(1<<ICF1)			;clear pending int
	out	TIFR1,temp
	
#if 0
	lds	temp,srx_state
	subi	temp,-'0'
	rcall	uartputc
	lds	temp,srx_dr
	rcall	printhex
#endif	
	lds	temp,srx_state
	cpi	temp,0
	brne	srxi_S1		

; State 0: Wait for start bit

;	sts	srx_lastedge,zl			;save beginning of start bit
;	sts	srx_lastedge+1,zh
	movw	srx_lastedgel,zl
	ldi	temp,1
	sts	srx_state,temp
	ldi	temp,2
	sts	srx_char_to,temp
	sbis	P_RXD-2,RXD			;RXD still low?
	rjmp	srxi_end2
	ldi	zl,(1<<ICNC1)|(1<<CS10)		;next edge is falling edge
	outm8	TCCR1B,zl
	ldi	zh,(1<<ICF1)			;clear pending int
	out	TIFR1,zh
	sts	srx_state,_0
	sts	srx_char_to,_0
	rjmp	srxi_end2

srxi_S1:
	cpi	temp,1
	brne	srxi_S2

; State 1: Check start bit (and collect 0-bits)

;	lds	temp,srx_lastedge
;	lds	temp2,srx_lastedge+1
;	sts	srx_lastedge,zl
;	sts	srx_lastedge+1,zh

	movw	temp,srx_lastedgel
	movw	srx_lastedgel,zl

	sub	zl,temp
	sbc	zh,temp2
	subi	zl,low ((SSER_BIT_TC+1)/2)
	sbci	zh,high((SSER_BIT_TC+1)/2)
	brcs	srxi_sberr

;	mov	temp,zh	
;	rcall	printhex
;	mov	temp,zl
;	rcall	printhex

	ldi	temp,0x80
srxi_1l:
	subi	zl,low(SSER_BIT_TC)
	sbci	zh,high(SSER_BIT_TC)
	brcs	srxi_1be
	lsr	temp
	brcc	srxi_1l
	rjmp	srxi_complete
srxi_1be:
	sts	srx_dr,temp
	ldi	temp,2
	sts	srx_state,temp
	rjmp	srxi_end2

srxi_sberr:
	ldi	temp,(1<<ICNC1)|(1<<CS10)	;next edge is falling edge
	outm8	TCCR1B,temp
	ldi	temp,(1<<ICF1)		;clear pending int
	out	TIFR1,temp
	sts	srx_state,_0		;next state
#if 1
	ldi	temp,'?'
	rcall	uartputc
	subi	zl,low (-(SSER_BIT_TC+1)/2)
	sbci	zh,high(-(SSER_BIT_TC+1)/2)
	mov	temp,zh
	rcall	printhex
	mov	temp,zl
	rcall	printhex
#endif
	rjmp	srxi_end2

srxi_S2:
	cpi	temp,2
	brne	srxi_S3

; State 2: collect 1-bits

;	lds	temp,srx_lastedge
;	lds	temp2,srx_lastedge+1
;	sts	srx_lastedge,zl
;	sts	srx_lastedge+1,zh

	movw	temp,srx_lastedgel
	movw	srx_lastedgel,zl

	sub	zl,temp
	sbc	zh,temp2
	subi	zl,low ((SSER_BIT_TC+1)/2)
	sbci	zh,high((SSER_BIT_TC+1)/2)

	lds	temp,srx_dr
srxi_2l:
	sec				;one more 1 bit
	ror	temp
	brcs	srxi_complete1		;8 bits recieved
	subi	zl,low(SSER_BIT_TC)
	sbci	zh,high(SSER_BIT_TC)
	brcc	srxi_2l
	
	sts	srx_dr,temp
	ldi	temp,3
	sts	srx_state,temp
	rjmp	srxi_end2
	
srxi_complete1:
	ldi	temp2,1			;We are in start bit now.
	sts	srx_state,temp2
	ldi	temp2,2
	sts	srx_char_to,temp2
	rjmp	srxi_complete
	
srxi_S3:
	cpi	temp,3
	brne	srxi_S4

; State 3: collect 0-bits

;	lds	temp,srx_lastedge
;	lds	temp2,srx_lastedge+1
;	sts	srx_lastedge,zl
;	sts	srx_lastedge+1,zh

	movw	temp,srx_lastedgel
	movw	srx_lastedgel,zl

	sub	zl,temp
	sbc	zh,temp2
	subi	zl,low ((SSER_BIT_TC+1)/2)
	sbci	zh,high((SSER_BIT_TC+1)/2)

	lds	temp,srx_dr
srxi_3l:
					;one more 0 bit
	lsr	temp
	brcs	srxi_complete0		;8 bits recieved
	subi	zl,low(SSER_BIT_TC)
	sbci	zh,high(SSER_BIT_TC)
	brcc	srxi_3l
	
	sts	srx_dr,temp
	ldi	temp,2
	sts	srx_state,temp
	rjmp	srxi_end2

srxi_S4:
	ldi	zl,(1<<ICNC1)|(1<<CS10)	;next edge is falling edge
	outm8	TCCR1B,zl
	ldi	zl,(1<<ICF1)		;clear pending int
	sts	srx_state,_0		;next state
	rjmp	srxi_end2

srxi_complete0:	
	sts	srx_char_to,_0		;clear timeout
	sts	srx_state,_0		;next state
srxi_complete:
#if 0
	ldi	zl,(1<<ICNC1)|(1<<CS10)	;next edge is falling edge
	outm8	TCCR1B,zl
	ldi	zl,(1<<ICF1)		;clear pending int
	out	TIFR1,zl
#endif

; Save received character in a circular buffer. Do nothing if buffer overflows.

	lds	zh,rxcount		;if rxcount < RXBUFSIZE
	cpi	zh,RXBUFSIZE		;   (room for at least 1 char?)
	brsh	srxi_ov			; 
	inc	zh			;
	sts	rxcount,zh		;   rxcount++

	ldi	zl,low(rxfifo)		;  
	lds	zh,rxidx_w		;
	add	zl,zh			;
	inc	zh			;
	andi	zh,RXBUFMASK		;
	sts	rxidx_w,zh		;   rxidx_w = ++rxidx_w % RXBUFSIZE
	ldi	zh,high(rxfifo)		;
	brcc	PC+2			;
	inc	zh			;
	st	z,temp			;   rxfifo[rxidx_w] = char
srxi_ov:					;endif

srxi_end2:
	pop	temp2
srxi_end: 
	pop	zl
	pop	zh
	pop	temp
	out	sreg,temp
	pop	temp
	reti


;----------------------------------------------------------------------

	.cseg

; Timer/Counter1 Compare Match A interrupt
	
	INTERRUPT OC1Aaddr
	
	push	temp
	in	temp,sreg
	push	temp
	push	zh

	inm8	temp,OCR1AL
	inm8	zh,OCR1AH
	subi	temp,low(-SSER_BIT_TC)
	sbci	zh,high(-SSER_BIT_TC)
	outm8	OCR1AH,zh
	outm8	OCR1AL,temp
	lds	temp,stx_bitcount
	tst	temp
	breq	stxi_nxtchar
	
	dec	temp
	sts	stx_bitcount,temp
	ldi	zh,9				;Start bit?
	cp	temp,zh
	ldi	zh,(1<<COM1A1)
	breq	stxi_0
	lds	temp,stx_dr
	sbrs	temp,0
	ldi	zh,(1<<COM1A1)|(1<<COM1A0)
	lsr	temp
	sts	stx_dr,temp
stxi_0:
	outm8	TCCR1A,zh
	pop	zh
	pop	temp
	out	sreg,temp
	pop	temp
	reti

; more characters?
stxi_nxtchar:
	lds	temp,txcount		;if txcount != 0
	tst	temp			;
	breq	stxi_dis
; get next char
	push	zl
	dec	temp			;
	sts	txcount,temp		;   --txcount
	ldi	zl,low(txfifo)		;  
	ldi	zh,high(txfifo)		;
	lds	temp,txidx_r		;
	add	zl,temp			;
	brcc	PC+2			;
	inc	zh			;
	inc	temp			;
	andi	temp,TXBUFMASK		;
	sts	txidx_r,temp		;
	ld	temp,z
	com	temp
	sts	stx_dr,temp
	ldi	temp,10
	sts	stx_bitcount,temp
	pop	zl
	pop	zh
	pop	temp
	out	sreg,temp
	pop	temp
	reti

; disable transmitter
stxi_dis:
	ldi	temp,(1<<COM1A1)|(1<<COM1A0)
	outm8	TCCR1A,temp
	inm8	temp,TIMSK1
	andi	temp,~(1<<OCIE1A)
	outm8	TIMSK1,temp
	pop	zh
	pop	temp
	out	sreg,temp
	pop	temp
	reti
;------------------------------------------------------------------

srx_to:
#if 0
	ldi	zl,(1<<ICNC1)|(1<<CS10)	;next edge is falling edge
	outm8	TCCR1B,zl
	ldi	zl,(1<<ICF1)		;clear pending int
	out	TIFR1,zl
#endif
	push	temp

#if 0
	ldi	temp,'|'
	rcall	uartputc
#endif
	lds	temp,srx_dr
	mov	zl,temp
	com	zl
	andi	zl,0x80
srxto_l:
	lsr	temp
	or	temp,zl
	brcc	srxto_l
	
; Save received character in a circular buffer. Do nothing if buffer overflows.

	lds	zh,rxcount		;if rxcount < RXBUFSIZE
	cpi	zh,RXBUFSIZE		;   (room for at least 1 char?)
	brsh	srxto_ov			; 
	inc	zh			;
	sts	rxcount,zh		;   rxcount++

	ldi	zl,low(rxfifo)		;  
	lds	zh,rxidx_w		;
	add	zl,zh			;
	inc	zh			;
	andi	zh,RXBUFMASK		;
	sts	rxidx_w,zh		;   rxidx_w = ++rxidx_w % RXBUFSIZE
	ldi	zh,high(rxfifo)		;
	brcc	PC+2			;
	inc	zh			;
	st	z,temp			;   rxfifo[rxidx_w] = char
srxto_ov:					;endif
	sts	srx_state,_0		;next state
	
	pop	temp
	ret
	
	
;Fetches a char from the buffer to temp. If none available, waits till one is.

uartgetc:
	lds	temp,rxcount		;Number of characters in buffer
	tst	temp
	breq	uartgetc		;Wait for char
	
	push	zh
	push	zl
	ldi	zl,low(rxfifo)
	ldi	zh,high(rxfifo)
	lds	temp,rxidx_r
	add	zl,temp
	brcc	PC+2
	inc	zh
	inc	temp
	andi	temp,RXBUFMASK
	sts	rxidx_r,temp
	cli
	lds	temp,rxcount
	dec	temp
	sts	rxcount,temp
	sei
	ld	temp,z		;don't forget to get the char
	pop	zl
	pop	zh
	ret

;Sends a char from temp to the soft uart. 

uartputc:
	push	zh
	push	zl
	in	zl,sreg
	push	zl
	push	temp
sputc_l:
	lds	temp,txcount		;do {
	cpi	temp,TXBUFSIZE		;
	brsh	sputc_l			;} while (txcount >= TXBUFSIZE)

	ldi	zl,low(txfifo)		;  
	ldi	zh,high(txfifo)		;
	lds	temp,txidx_w		;
	add	zl,temp			;
	brcc	PC+2			;
	inc	zh			;
	inc	temp			;
	andi	temp,TXBUFMASK		;
	sts	txidx_w,temp		;   txidx_w = ++txidx_w % TXBUFSIZE
	pop	temp			;
	st	z,temp			;   txfifo[txidx_w] = char
	cli
	lds	zh,txcount
	inc	zh
	sts	txcount,zh
	dec	zh
	brne	sputc_e
; Enable transmitter
	inm8	zh,TIMSK1
	ori	zh,(1<<OCIE1A)
	outm8	TIMSK1,zh
sputc_e:
	pop	zl
	out	sreg,zl
	pop	zl
	pop	zh
	ret


; Wait, till tx buffer is empty.

uart_wait_empty:
	push	temp
uwe_loop:
	lds	temp,txcount
	tst	temp
	brne	uwe_loop
	pop	temp
	ret


; vim:set ts=8 noet nowrap
Commit	Line	Data
9c15f366 L	1	; Serial interface using the ATmega8/88 USART.
	2	; This is part of the Z80-CP/M emulator written by Sprite_tm.
	3	;
	4	; Copyright (C) 2010 Leo C.
	5	;
	6	; This file is part of avrcpm.
	7	;
	8	; avrcpm is free software: you can redistribute it and/or modify it
	9	; under the terms of the GNU General Public License as published by
	10	; the Free Software Foundation, either version 3 of the License, or
	11	; (at your option) any later version.
	12	;
	13	; avrcpm is distributed in the hope that it will be useful,
	14	; but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	16	; GNU General Public License for more details.
	17	;
	18	; You should have received a copy of the GNU General Public License
	19	; along with avrcpm. If not, see <http://www.gnu.org/licenses/>.
	20	;
	21	; $Id$
	22	;
	23
	24	#define SSER_BIT_TC (F_CPU+BAUD/2) / BAUD
	25
	26	#define RXBUFMASK RXBUFSIZE-1
	27	#define TXBUFMASK TXBUFSIZE-1
	28
	29	.dseg
	30
	31	srx_state:
	32	.byte 1
	33	srx_char_to:
	34	.byte 1
	35	srx_dr:
	36	.byte 1
	37	;srx_lastedge:
	38	; .byte 2
	39	stx_bitcount:
	40	.byte 1
	41	stx_dr:
	42	.byte 1
	43	rxcount:
	44	.byte 1
	45	rxidx_w:
	46	.byte 1
	47	rxidx_r:
	48	.byte 1
	49	txcount:
	50	.byte 1
	51	txidx_w:
	52	.byte 1
	53	txidx_r:
	54	.byte 1
	55	rxfifo:
	56	.byte RXBUFSIZE
	57	txfifo:
	58	.byte TXBUFSIZE
	59
	60
	61	.cseg
	62
	63	; Init
	64	uart_init:
65
66	; - Init clock/timer system and serial port
67
68	; Init timer 1 as
69	; - Soft UART TX (OC1A/OCR1A).
70	; - Soft UART RX (ICP1/ICR1).
71	; - 1ms System timer is already configured at this point.
72
73	ldi temp,(1<<COM1A1)\|(1<<COM1A0) ;OC1A high on compare match (UART TX)
74	outm8 TCCR1A,temp
75
76	ldi temp,(1<<ICF1) ;clear pending int
77	out TIFR1,temp
78	inm8 temp,TIMSK1
79	ori temp,(1<<ICIE1) ;Enable input capture int. (UART RX)
80	outm8 TIMSK1,temp
81	ret
82
83	;------------------------------------------------------------------
84
85	.cseg
9c15f366	86
4675c141 L	87	; Timer/Counter1 Input Capture interrupt
	88
	89	INTERRUPT ICP1addr
9c15f366 L	90
	91	push temp
	92	in temp,sreg
	93	push temp
	94	push zh
	95	push zl
	96	inm8 zl,ICR1L
	97	inm8 zh,ICR1H
	98	push temp2
	99	ldi temp2,(1<<ICES1)
	100	inm8 temp,TCCR1B
	101	eor temp,temp2 ;toggle edge
	102	outm8 TCCR1B,temp
	103	ldi temp,(1<<ICF1) ;clear pending int
	104	out TIFR1,temp
	105
	106	#if 0
	107	lds temp,srx_state
	108	subi temp,-'0'
	109	rcall uartputc
	110	lds temp,srx_dr
	111	rcall printhex
	112	#endif
	113	lds temp,srx_state
	114	cpi temp,0
	115	brne srxi_S1
	116
	117	; State 0: Wait for start bit
	118
	119	; sts srx_lastedge,zl ;save beginning of start bit
	120	; sts srx_lastedge+1,zh
	121	movw srx_lastedgel,zl
	122	ldi temp,1
	123	sts srx_state,temp
	124	ldi temp,2
	125	sts srx_char_to,temp
	126	sbis P_RXD-2,RXD ;RXD still low?
	127	rjmp srxi_end2
	128	ldi zl,(1<<ICNC1)\|(1<<CS10) ;next edge is falling edge
	129	outm8 TCCR1B,zl
	130	ldi zh,(1<<ICF1) ;clear pending int
	131	out TIFR1,zh
	132	sts srx_state,_0
	133	sts srx_char_to,_0
	134	rjmp srxi_end2
	135
	136	srxi_S1:
	137	cpi temp,1
	138	brne srxi_S2
	139
	140	; State 1: Check start bit (and collect 0-bits)
	141
	142	; lds temp,srx_lastedge
	143	; lds temp2,srx_lastedge+1
	144	; sts srx_lastedge,zl
	145	; sts srx_lastedge+1,zh
	146
	147	movw temp,srx_lastedgel
	148	movw srx_lastedgel,zl
	149
	150	sub zl,temp
	151	sbc zh,temp2
	152	subi zl,low ((SSER_BIT_TC+1)/2)
	153	sbci zh,high((SSER_BIT_TC+1)/2)
154	brcs srxi_sberr
155
156	; mov temp,zh
157	; rcall printhex
158	; mov temp,zl
159	; rcall printhex
160
161	ldi temp,0x80
162	srxi_1l:
163	subi zl,low(SSER_BIT_TC)
164	sbci zh,high(SSER_BIT_TC)
165	brcs srxi_1be
166	lsr temp
167	brcc srxi_1l
168	rjmp srxi_complete
169	srxi_1be:
170	sts srx_dr,temp
171	ldi temp,2
172	sts srx_state,temp
173	rjmp srxi_end2
174
175	srxi_sberr:
176	ldi temp,(1<<ICNC1)\|(1<<CS10) ;next edge is falling edge
177	outm8 TCCR1B,temp
178	ldi temp,(1<<ICF1) ;clear pending int
179	out TIFR1,temp
180	sts srx_state,_0 ;next state
181	#if 1
182	ldi temp,'?'
183	rcall uartputc
184	subi zl,low (-(SSER_BIT_TC+1)/2)
185	sbci zh,high(-(SSER_BIT_TC+1)/2)
186	mov temp,zh
187	rcall printhex
188	mov temp,zl
189	rcall printhex
190	#endif
191	rjmp srxi_end2
192
193	srxi_S2:
194	cpi temp,2
195	brne srxi_S3
196
197	; State 2: collect 1-bits
198
199	; lds temp,srx_lastedge
200	; lds temp2,srx_lastedge+1
201	; sts srx_lastedge,zl
202	; sts srx_lastedge+1,zh
203
204	movw temp,srx_lastedgel
205	movw srx_lastedgel,zl
206
207	sub zl,temp
208	sbc zh,temp2
209	subi zl,low ((SSER_BIT_TC+1)/2)
210	sbci zh,high((SSER_BIT_TC+1)/2)
211
212	lds temp,srx_dr
213	srxi_2l:
214	sec ;one more 1 bit
215	ror temp
216	brcs srxi_complete1 ;8 bits recieved
217	subi zl,low(SSER_BIT_TC)
218	sbci zh,high(SSER_BIT_TC)
219	brcc srxi_2l
220
221	sts srx_dr,temp
222	ldi temp,3
223	sts srx_state,temp
224	rjmp srxi_end2
225
226	srxi_complete1:
227	ldi temp2,1 ;We are in start bit now.
228	sts srx_state,temp2
229	ldi temp2,2
230	sts srx_char_to,temp2
231	rjmp srxi_complete
232
233	srxi_S3:
234	cpi temp,3
235	brne srxi_S4
236
237	; State 3: collect 0-bits
238
239	; lds temp,srx_lastedge
240	; lds temp2,srx_lastedge+1
241	; sts srx_lastedge,zl
242	; sts srx_lastedge+1,zh
243
244	movw temp,srx_lastedgel
245	movw srx_lastedgel,zl
246
247	sub zl,temp
248	sbc zh,temp2
249	subi zl,low ((SSER_BIT_TC+1)/2)
250	sbci zh,high((SSER_BIT_TC+1)/2)
251
252	lds temp,srx_dr
253	srxi_3l:
254	;one more 0 bit
255	lsr temp
256	brcs srxi_complete0 ;8 bits recieved
257	subi zl,low(SSER_BIT_TC)
258	sbci zh,high(SSER_BIT_TC)
259	brcc srxi_3l
260
261	sts srx_dr,temp
262	ldi temp,2
263	sts srx_state,temp
264	rjmp srxi_end2
265
266	srxi_S4:
267	ldi zl,(1<<ICNC1)\|(1<<CS10) ;next edge is falling edge
268	outm8 TCCR1B,zl
269	ldi zl,(1<<ICF1) ;clear pending int
270	sts srx_state,_0 ;next state
271	rjmp srxi_end2
272
273	srxi_complete0:
274	sts srx_char_to,_0 ;clear timeout
275	sts srx_state,_0 ;next state
276	srxi_complete:
277	#if 0
278	ldi zl,(1<<ICNC1)\|(1<<CS10) ;next edge is falling edge
279	outm8 TCCR1B,zl
280	ldi zl,(1<<ICF1) ;clear pending int
281	out TIFR1,zl
282	#endif
283
284	; Save received character in a circular buffer. Do nothing if buffer overflows.
285
286	lds zh,rxcount ;if rxcount < RXBUFSIZE
287	cpi zh,RXBUFSIZE ; (room for at least 1 char?)
288	brsh srxi_ov ;
289	inc zh ;
290	sts rxcount,zh ; rxcount++
291
292	ldi zl,low(rxfifo) ;
293	lds zh,rxidx_w ;
294	add zl,zh ;
295	inc zh ;
296	andi zh,RXBUFMASK ;
297	sts rxidx_w,zh ; rxidx_w = ++rxidx_w % RXBUFSIZE
298	ldi zh,high(rxfifo) ;
299	brcc PC+2 ;
300	inc zh ;
301	st z,temp ; rxfifo[rxidx_w] = char
302	srxi_ov: ;endif
303
304	srxi_end2:
305	pop temp2
306	srxi_end:
307	pop zl
308	pop zh
309	pop temp
310	out sreg,temp
311	pop temp
312	reti
313
314
315	;----------------------------------------------------------------------
316
317	.cseg
9c15f366	318
4675c141 L	319	; Timer/Counter1 Compare Match A interrupt
	320
	321	INTERRUPT OC1Aaddr
9c15f366 L	322
	323	push temp
	324	in temp,sreg
	325	push temp
	326	push zh
	327
	328	inm8 temp,OCR1AL
	329	inm8 zh,OCR1AH
	330	subi temp,low(-SSER_BIT_TC)
	331	sbci zh,high(-SSER_BIT_TC)
	332	outm8 OCR1AH,zh
	333	outm8 OCR1AL,temp
	334	lds temp,stx_bitcount
	335	tst temp
	336	breq stxi_nxtchar
	337
	338	dec temp
	339	sts stx_bitcount,temp
	340	ldi zh,9 ;Start bit?
	341	cp temp,zh
	342	ldi zh,(1<<COM1A1)
	343	breq stxi_0
	344	lds temp,stx_dr
	345	sbrs temp,0
	346	ldi zh,(1<<COM1A1)\|(1<<COM1A0)
	347	lsr temp
	348	sts stx_dr,temp
	349	stxi_0:
	350	outm8 TCCR1A,zh
	351	pop zh
	352	pop temp
	353	out sreg,temp
	354	pop temp
	355	reti
	356
	357	; more characters?
	358	stxi_nxtchar:
	359	lds temp,txcount ;if txcount != 0
	360	tst temp ;
	361	breq stxi_dis
	362	; get next char
	363	push zl
	364	dec temp ;
	365	sts txcount,temp ; --txcount
	366	ldi zl,low(txfifo) ;
	367	ldi zh,high(txfifo) ;
	368	lds temp,txidx_r ;
	369	add zl,temp ;
	370	brcc PC+2 ;
	371	inc zh ;
	372	inc temp ;
	373	andi temp,TXBUFMASK ;
	374	sts txidx_r,temp ;
	375	ld temp,z
	376	com temp
	377	sts stx_dr,temp
	378	ldi temp,10
	379	sts stx_bitcount,temp
	380	pop zl
	381	pop zh
	382	pop temp
	383	out sreg,temp
	384	pop temp
	385	reti
386
387	; disable transmitter
388	stxi_dis:
389	ldi temp,(1<<COM1A1)\|(1<<COM1A0)
390	outm8 TCCR1A,temp
391	inm8 temp,TIMSK1
392	andi temp,~(1<<OCIE1A)
393	outm8 TIMSK1,temp
394	pop zh
395	pop temp
396	out sreg,temp
397	pop temp
398	reti
399	;------------------------------------------------------------------
400
401	srx_to:
402	#if 0
403	ldi zl,(1<<ICNC1)\|(1<<CS10) ;next edge is falling edge
404	outm8 TCCR1B,zl
405	ldi zl,(1<<ICF1) ;clear pending int
406	out TIFR1,zl
407	#endif
408	push temp
409
410	#if 0
411	ldi temp,'\|'
412	rcall uartputc
413	#endif
414	lds temp,srx_dr
415	mov zl,temp
416	com zl
417	andi zl,0x80
418	srxto_l:
419	lsr temp
420	or temp,zl
421	brcc srxto_l
422
423	; Save received character in a circular buffer. Do nothing if buffer overflows.
424
425	lds zh,rxcount ;if rxcount < RXBUFSIZE
426	cpi zh,RXBUFSIZE ; (room for at least 1 char?)
427	brsh srxto_ov ;
428	inc zh ;
429	sts rxcount,zh ; rxcount++
430
431	ldi zl,low(rxfifo) ;
432	lds zh,rxidx_w ;
433	add zl,zh ;
434	inc zh ;
435	andi zh,RXBUFMASK ;
436	sts rxidx_w,zh ; rxidx_w = ++rxidx_w % RXBUFSIZE
437	ldi zh,high(rxfifo) ;
438	brcc PC+2 ;
439	inc zh ;
440	st z,temp ; rxfifo[rxidx_w] = char
441	srxto_ov: ;endif
442	sts srx_state,_0 ;next state
443
444	pop temp
445	ret
446
447
448	;Fetches a char from the buffer to temp. If none available, waits till one is.
449
450	uartgetc:
451	lds temp,rxcount ;Number of characters in buffer
452	tst temp
453	breq uartgetc ;Wait for char
454
455	push zh
456	push zl
457	ldi zl,low(rxfifo)
458	ldi zh,high(rxfifo)
459	lds temp,rxidx_r
460	add zl,temp
461	brcc PC+2
462	inc zh
463	inc temp
464	andi temp,RXBUFMASK
465	sts rxidx_r,temp
466	cli
467	lds temp,rxcount
468	dec temp
469	sts rxcount,temp
470	sei
471	ld temp,z ;don't forget to get the char
472	pop zl
473	pop zh
474	ret
475
476	;Sends a char from temp to the soft uart.
477
478	uartputc:
479	push zh
480	push zl
481	in zl,sreg
482	push zl
483	push temp
484	sputc_l:
485	lds temp,txcount ;do {
486	cpi temp,TXBUFSIZE ;
487	brsh sputc_l ;} while (txcount >= TXBUFSIZE)
488
489	ldi zl,low(txfifo) ;
490	ldi zh,high(txfifo) ;
491	lds temp,txidx_w ;
492	add zl,temp ;
493	brcc PC+2 ;
494	inc zh ;
495	inc temp ;
496	andi temp,TXBUFMASK ;
497	sts txidx_w,temp ; txidx_w = ++txidx_w % TXBUFSIZE
498	pop temp ;
499	st z,temp ; txfifo[txidx_w] = char
500	cli
501	lds zh,txcount
502	inc zh
503	sts txcount,zh
504	dec zh
505	brne sputc_e
506	; Enable transmitter
507	inm8 zh,TIMSK1
508	ori zh,(1<<OCIE1A)
509	outm8 TIMSK1,zh
510	sputc_e:
511	pop zl
512	out sreg,zl
513	pop zl
514	pop zh
515	ret
516
517
518	; Wait, till tx buffer is empty.
519
520	uart_wait_empty:
521	push temp
522	uwe_loop:
523	lds temp,txcount
524	tst temp
525	brne uwe_loop
526	pop temp
527	ret
528
529
530	; vim:set ts=8 noet nowrap
531