Z85233 Datasheet, PDF (279/317 Pages) Zilog, Inc. – The Zilog SCC Serial Communication Controller

Application Note
Technical Considerations When Implementing LocalTalk Link Access Protocol
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0000044d f5
0000044e d5
0000044f e5
00000450 dbe9
00000452 2aWwww
00000455 77
00000456 23
00000457 22Www
0000045a ed5bWwww
0000045e af
0000045f ed52
00000461 c2Wwww
00000464 21Wwww
00000467 cbc6
00000469
00000469 3e38
0000046b d3e8
0000046d e1
0000046e d1
0000046f f1
00000470 fb
00000471 c9
00000472
00000472 f5
00000473 c5
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1131
1132
1133
1134
1135
1136
1137recint:
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
push
push
push
in
ld
ld
inc
ld
ld
xor
sbc
jp
1150
ld
1151
set
1152
1153recexit:
1154
ld
1155
out
1156
pop
1157
pop
1158
pop
1159
ei
1160
ret
1161
1162
1163
1164
1165
1166
1167;
1168;
1169;
1170;
1171
1172 spcond:
1173
push
1174
push
1175
push
1176
1177
ld
1178
out
1179
in
1180
and
1181
jp
1182
;
1183
ld
1184
set
1185
jp
LISTING 3
;******************************
;receive int service routine.
;******************************
;save received character in receiver buffer
;to by rxpointer
af
de
hl
a,(scc_data)
hl,(rxpointer)
(hl),a
hl
(rxpointer),hl
de,(rxbufend)
a
hl,de
nz,recexit
hl,recerrflg
0,(hl)
a,038h
(scc_cont),a
hl
de
af
;save af
;read scc data
;
;save it
;update pointer
;
;end of rx buffer
;reset cy
;
;if not zero,then receive
byte length is ok
;
;set bit0=1 maxfrmflg to indicate error
;because of max frame
size exceeded.
;reset highest ius
;restore af
;enable int
;return from int
;note ret and not reti is used for scc
;interrupts on the z80181.
;*********************************************
;special receive interrupt service routine
;*********************************************
“parity is special condition” bit is off.
special conditions are eof or rx overrun error.
crc error flag is valid only if eof is valid.
if frame is ok then recerrflg bit1=0, otherwise
af
bc
hl;
a,01h
(scc_cont),a
a,(scc_cont)
01100000b
z,ok
hl,recerrflg
1,(hl)
crc_exit
;save af reg
;
;read rr1
;check bit6 (crc) or bit5 (overrun)
;
;fetch receive error flag
;set bit1=1 for frame not ok
6-144
UM010901-0601