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comparison level1/modules/dwread.asm @ 2182:b1b374ada668

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Added 38.4kbps routines from Darren Atkinson
author boisy
date Sun, 08 Mar 2009 14:11:52 +0000
parents 660cc987e18d
children 27f07aa0bca0
comparison
equal deleted inserted replaced
2181:c34956608086 2182:b1b374ada668
1 IFNE H6309-1 1 IFNE BAUD38400
2
3 ******************************************************************************
4 * COCO 38400 BAUD BIT-BANGER RECEIVER
5 ******************************************************************************
6 *
7 * WAITS FOR A SPECIFIED TIMEOUT PERIOD UNTIL A START-BIT APPEARS ON THE
8 * BIT-BANGER INPUT. DATA RECEPTION IS INITIATED IF A START-BIT APPEARS
9 * BEFORE THE TIMEOUT PERIOD EXPIRES. THE SERIAL DATA FORMAT MUST BE:
10 * 1 START BIT, 8 DATA BITS, NO PARITY, 1..2 STOP BITS.
11 *
12 * DATA RECPEPTION TERMINATES WHEN:
13 * - A PERIOD OF 4 MS ELLAPSES WITHOUT A NEW START BIT
14 * - A FRAMING ERROR IS DETECTED.
15 *
16 * ON ENTRY:
17 * X = ADDRESS FOR DATA STORAGE
18 * A = TIMEOUT VALUE (125 = APPROX ONE SECOND)
19 *
20 * ON EXIT:
21 * Y = DATA CHECKSUM
22 * D = NUMBER OF BYTES RECEIVED
23 * X AND U ARE PRESERVED
24 * CC.CARRY IS SET ONLY IF A FRAMING ERROR WAS DETECTED
25 *
26 ******************************************************************************
27 BBIN EQU $FF22 ; BIT-BANGER INPUT ADDRESS
28 BUFBAS EQU 1 ; OFFSET TO STORAGE ADDRESS ON STACK
29
30 DWRead
31 RCV38K CLRB ; CLEAR CARRY FLAG (NO FRAMING ERROR)
32 PSHS U,X,CC ; PRESERVE REGISTERS
33 ORCC #$50 ; MASK INTERRUPTS
34 TFR D,Y ; SET Y TO INITIAL TIMEOUT COUNTER
35 LEAU ,X ; POINT U TO STORAGE BUFFER
36 LDX #0 ; INITIALIZE CHECKSUM
37 LDA #1 ; A = SERIAL INPUT MASK
38
39 WAIT1 LEAY ,Y ; TEST TIMEOUT COUNTER
40 BEQ FINISH ; BRANCH IF TIMEOUT HAS EXPIRED
41 WAIT2 BITA BBIN ; CHECK FOR START BIT
42 BEQ BSTART ; BRANCH IF START BIT DETECTED
43 LEAY -1,Y ; DECREMENT TIMEOUT COUNTER
44 BITA BBIN ; CHECK FOR START BIT
45 BNE WAIT1 ; LOOP IF STILL NO START BIT
46
47 BSTART LDY #BBIN ; POINT Y TO BIT BANGER INPUT REGISTER
48 LEAU ,U ; 4 CYCLE DELAY
49 LDB #$7F ; INITIALIZE B FOR SHIFT COUNTER
50 RDLOOP TST ,Y++ ; 9 CYCLE DELAY
51 LDA ,--Y ; READ DATA BIT
52 LSRA ; SHIFT DATA INTO CARRY
53 RORB ; ROTATE INTO BYTE ACCUMULATOR
54 BCS RDLOOP ; LOOP UNTIL 8 DATA BITS HAVE BEEN READ
55
56 STB ,U+ ; STORE RECEIVED BYTE
57 ABX ; ACCUMULATE CHECKSUM
58 CLRA ; DO THE EQUIVALENT OF..
59 INCA ; ..LDA #1 USING 4 CYCLES
60 ANDA ,Y ; CHECK FOR THE STOP BIT
61 LDY #128 ; SET TIMEOUT COUNTER TO 4MS
62 TSTA ; IF STOP BIT IS GOOD THEN..
63 BNE WAIT2 ; ..GO WAIT FOR NEXT BYTE
64
65 FINISH INCA ; A=1 IF FRAMING ERROR, 2 OTHERWISE
66 ORA ,S ; SETS CARRY BIT IN CC VALUE ON..
67 STA ,S ; ..STACK IF FRAMING ERROR DETECTED
68 LEAY ,X ; RETURN CHECKSUM IN Y
69 TFR U,D ; CALCULATE NUMBER..
70 SUBD BUFBAS,S ; ..OF BYTES RECEIVED
71 PULS CC,X,U,PC ; RESTORE REGISTERS AND RETURN
72
73 ELSE
74 IFNE H6309-1
2 ** 75 **
3 ** Rev 3 Notes: 76 ** Rev 3 Notes:
4 ** 77 **
5 ** For CoCo 1,2 or 3 78 ** For CoCo 1,2 or 3
6 ** 6809 Timing 79 ** 6809 Timing
113 SUBD BUFBAS,S ; ..OF BYTES RECEIVED 186 SUBD BUFBAS,S ; ..OF BYTES RECEIVED
114 LEAS 2,S ; POP TIMEOUT AND BIT LOOP COUNTERS 187 LEAS 2,S ; POP TIMEOUT AND BIT LOOP COUNTERS
115 PULS CC,DP,X,U,PC ; RESTORE REGISTERS AND RETURN 188 PULS CC,DP,X,U,PC ; RESTORE REGISTERS AND RETURN
116 SETDP $00 189 SETDP $00
117 190
118 191 ELSE
119
120
121
122
123
124
125 ELSE
126
127
128 192
129 ** Rev 4 Notes: 193 ** Rev 4 Notes:
130 ** 194 **
131 ** For CoCo 2 or 3 195 ** For CoCo 2 or 3
132 ** 6309 Native Mode 196 ** 6309 Native Mode
222 TFR Y,D ; CALCULATE ACTUAL NUMBER.. 286 TFR Y,D ; CALCULATE ACTUAL NUMBER..
223 SUBD BUFBAS,S ; ..OF BYTES RECEIVED 287 SUBD BUFBAS,S ; ..OF BYTES RECEIVED
224 LEAY ,X ; RETURN CHECKSUM IN Y 288 LEAY ,X ; RETURN CHECKSUM IN Y
225 PULS CC,X,U,PC ; RESTORE REGISTERS AND RETURN 289 PULS CC,X,U,PC ; RESTORE REGISTERS AND RETURN
226 290
227 ENDC 291 ENDC
228 292 ENDC
229 293