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comparison bootman/llio_6551.a @ 2163:2db06bc0742a

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Start of BootMan
author boisy
date Tue, 20 May 2008 14:43:00 +0000
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2162:755b1b8ea019 2163:2db06bc0742a
1 NAM llio_coco3
2 TTL CoCo 3 low-level I/O handler
3
4 PSECT llio_coco3,0,0,0,0,llio
5
6 VSECT
7 ENDSECT
8
9 llio:
10 lbsr llinit
11 lbsr llread
12 lbsr llwrite
13 lbsr llterm
14
15 ********** I/O ROUTINES **********
16
17 * 6551 Parameters
18 ADDR EQU $FF68
19
20 A_RXD EQU ADDR+$00
21 A_TXD EQU ADDR+$00
22 A_STATUS EQU ADDR+$01
23 A_RESET EQU ADDR+$01
24 A_CMD EQU ADDR+$02
25 A_CTRL EQU ADDR+$03
26
27 * Baud rates
28 _B2400 EQU $1A 2400 bps, 8-N-1
29 _B4800 EQU $1C 4800 bps, 8-N-1
30 _B9600 EQU $1E 9600 bps, 8-N-1
31 _B19200 EQU $1F 19200 bps, 8-N-1
32
33 BAUD EQU _B9600
34
35 * ll_init - Initialize the low-level I/O
36 * Exit: Carry = 0: Init success; Carry = 1; Init failed
37 llinit
38 sta A_RESET soft reset (value not important)
39 * Set specific modes and functions:
40 * - no parity, no echo, no Tx interrupt
41 * - no Rx interrupt, enable Tx/Rx
42 lda #$0B
43 sta A_CMD save to command register
44 lda #BAUD
45 sta A_CTRL select proper baud rate
46 * Read any junk rx byte that may be in the register
47 lda A_RXD
48 rts
49
50
51 * llread - Read one character from 6551
52 *
53 * Entry: None
54 * Exit: A = character that was read
55 *
56 * Note, this routine currently doesn't timeout
57 llread
58 r lda A_STATUS get status byte
59 anda #$08 mask rx buffer status flag
60 beq r loop if rx buffer empty
61 lda A_RXD get byte from ACIA data port
62 rts
63
64 * llwrite - Write one character to 6551
65 *
66 * Entry: A = character to write
67 * Exit: None
68 llwrite
69 pshs a save byte to write
70 w lda A_STATUS get status byte
71 anda #$10 mask tx buffer status flag
72 beq w loop if tx buffer full
73 puls a get byte
74 sta A_TXD save to ACIA data port
75 rts
76
77
78 llterm
79 rts
80
81 IFNE 0
82 * llwout - Write an entire string
83 * llwerr - Write an entire string
84 llwerr
85 llwout
86 pshs a
87 l@ lda ,x+
88 cmpa #C$CR
89 beq e@
90 leay -1,y
91 beq f@
92 bsr Write
93 bra l@
94 e@ bsr Write
95 lda #C$LF
96 bsr Write
97 f@ ldx <buffptr
98 clrb
99 puls a,pc
100
101 * ReadLine - Read an entire string, up to CR
102 * Entry: X = address to place string being read (CR terminated)
103 * Y = maximum number of bytes to read (including nul byte)
104 ReadLine
105 ldx <buffptr
106 pshs y,x,a
107 ldy #80
108 l@ bsr Read read 1 character
109 cmpa #C$CR carriage return?
110 beq e@ branch if so...
111 cmpa #$08 backspace?
112 beq bs@
113 cmpy #$0000 anymore room?
114 beq l@
115 leay -1,y back up one char
116 sta ,x+ and save in input buffer
117 m@ bsr Write echo back out
118 bra l@
119 e@ sta ,x
120 bsr Write
121 lda #C$LF
122 bsr Write
123 clrb
124 puls a,x,y,pc
125 bs@ cmpx 1,s are we at start
126 beq l@ if so, do nothing
127 clr ,-x else erase last byte
128 lbsr Write write backspace
129 lda #C$SPAC a space...
130 lbsr Write write it
131 leay 1,y count back up free char
132 lda #$08 another backspace
133 bra m@
134 ENDC
135
136 endsect