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第一节 串行接口与通信. 本节重点:串行接口与通信概述,串行通信接口,通信规程和通信标准. 串行接口与通信概述. 一、并行通信与串行通信 数据通信的基本方式可分为 并行通信 与 串行通信 两 种: 并行通信: 用多条数据传输线将数据的各位同时传送。 特点:传输速度快,适用于短距离通信。 串行通信 :用一条传输线将数据一位一位地顺序传送。 特点:通信线路简单,利用电话或电报线路就可实现通信,适用于远距离通信,但传输速度慢. 二、串行通信方式 串行通信:分为 同步通信 (SYNC) 与 异步通信 ( ASYNC ) 两 种方式。 1 、异步通信及其协议 - PowerPoint PPT Presentation
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(SYNC)ASYNC1
0 45678ASCII 1()() 11.52 1
120/10101201200/1200
2
(bit)HDLC()EBCDASCIIIBM(BSC)
a b c
(1)(2) ABBA(3)
1
2(MODEM)()
(DTE)MODEM(DCE)1RS-232C RS-232CD259
RS-232CMODEMRS-232C
RS-232C259. TXD2MODEM RXD3RTS*4MODEMCTS*5
DSR*6(MODEM) CD8()MODEM RI22MODEMDTR*20RIMODEMGND7
RS-232CEIA1-3V~-15v0+3V~+15V EIATTL MCl488TTLEIAMCl489EIAITLRS-232C
2RS-423ARS-232CRS-232C1987RS-423A RS-423A
3RS-422ARS-422A
RS-422A2v0.2v25v
4RS-485RS-485
12RS-232C3RS-232CTTL4Modem
8251A8251A8251A 8251A 8251A8251A
8251A8251A8251A10~64K0~19.2K256788251A/
35678116641/11152 45
8251A
1 TXD12
CPU8251ATXRDYCPU8CPUTXE
2RXDRXD 8251ARXRDYCPU
8251ARXDRXD8251ASYNDET
SYNDET RXDRXRDY
3 CPU8251A38CPU8251ACPU8251A
4/(1)8251A(2)8251A (3)/C/ (4)CLK8251A RESET8251A58251A
251A
1251ACPU CS*CPUD7-D08CPU8251A8251ACPU
/RD* CPU8251AWR* CPU8251AC/D*//8251A/RD*WR*C/D*38251A
(4) TXRDYCPU8251A TXETXE8251A RXRDY8251ACPURXRDYRXRDY SYNDET
28251A(1) DTR*CPU DSR* RTS*CPU CTS*8251A43
TXDCPU8251ATXD RXD8251A
3 CLK8251A304.5 TXDTXCTXC11664
RXD:TXCRXCTXCCLK VCC GND
8251ACPU8251ACPU
2
8251A MOV DX0FFF2H L IN ALDX AND AL02H Dl1 JZ L MOV DX OFFF0H IN Al DX
48251A 128251A(3) CPU
8251A1 8251A()167/200E2H00E4H11111010B 0FAH00110111B 37H
MOV AL 0FAH MOV DX00E2HOUT DX AL 7/2 MOV AL37H OUT DX AL RTS*DTR*
2 52H216H7/00111000B 38H10010111B 97H8251A38251A8251ACPU
MOV AL38H 2OUT 52HAL 7MOV AL16H OUT 52HAL 16HOUT 52HAL MOV AL 97H OUT 52H AL
3 8251A80 8251A52H50HBUFFER
MOV AL0FAH 16 OUT 52HAL 72 MOV AL35H OUT 52HAL MOV DI0 MOV CX80 80
BEGININ AL52H RXRDY10TEST AL02H JZ BEGIN IN AL50 MOV DXOFFSET BUFFERMOV [DX+DI]ALINC DI IN AL52H TEST AL38H /
JZ ERROR LOOP BEGIN JMP EXIT 80ERROR CALL ERR-OUT EXIT
48251A
CPUTXRDY8251ACPURXRDY8251A
STT MOV DX8251A MOV AL7FH OUT DXAL 825lA81 MOV AL11H 64OUT DXALMOV DI MOV CX
NEXTMOV DX8251A IN ALDX AND AL01H TXRDY? JZ NEXT MOV DX8251A MOV AL[DI]8251A OUT DXAL INC DI LOOP NEXT HLT
SRRMOV DX8251A MOV AL7FH OUT DXAL 8251A8MOV AL 14H 164OUT DXAL MOV DI MOV CX
COMT MOV DX8251A IN ALDX ROR AL1 RXRDY? ROR AL1 JNC COMT ROR AL1 ROR AL1 JC ERR
MOV DX8251A IN ALDX MOV [DI]AL INC DI LOOP COMT HLT ERR CALL ERR-OUT
182512825138251
48251716482513FBH/3F8H58251A38.4KHzRTS*CTS*8251A02C0H02C1H71600B/s816H
I/OCPUI/OI/O CPUI/O/CPU
1/CPU/
2/////
I/O1CPUI/O CPU(READY)BUSY CPU
2I/OCPUI/OCPUI/OCPU
/CPU//
3.CPU/I/0(M/IO*)1-2/
12CPU
8255A 8255A8255A8255A
Intel 8255AI/OIntel
8255A8255A1ABC I/OA8I/O/B8I/OC8I/O4I/O
8255A
2ABCPU8255ACPU8255AC/AAC4BBC4
388255A/CPU8255A4//8255ARESETA0A1
8255ACPU1CPUD0-D78RESET8255AABC
CS*RD*8255ACPUWR*CPU8255AA1A08255A8255A4ABC
8255A
2 PA0~PA7 PB0~PB7 PC0~PC7 8255A 8255A0/ABC1/A B2/A
10/ABCI/O0
21 I/OAB8I/OC6AB20 (1) 1CPC3-PC5APC0-PC2BPC6~PC70
1
STB*8255AIBFSTBINTRINTRSTBIBFINTEINTEAPC4BPC0 ABSTB* PC4PC2IBFPC5PC1INTR PC3PC0INTE PC41PC21
(2) 1
OBF*CPU8255A8255AACK*OBF*8255AINTRINTRACKOBFINTEINTEAPC6BPC2 A BOBF* PC7 PC1ACK* PC6 PC2INTR PC3 PC0INTE PC61 PC21
32I/OAC5A30B121
12 STB* PC4IBFPC5OBF*PC7ACK* PC6INTR PC3(2) 22
(3) 2 20 11XXX01T 2011XXX00T 2111XXX11X 2111XXX10X XT10
8255A18255A8255AC/18255A8255A
8255A
1 8255AA0B0C40C40 10010001 91H MOV AL 91H OUT CTRL_PORTAL(2) C//1/
/
A2 PC4PC6B1PC2 MOV AL0C4H OUT CTRL_PORTAL MOV AL09H OUT CTRL_PORTALPC4A MOV ALODH OUT CTRL_PORTALPC6A MOV AL 05HOUT CTRL_PORTALPC2B
23 8255AA0BUFFCPU8088
BUSYACKBUSY
PC0PC0/PC7BUSY8255A10001000 88H A0C00PC0: 00000001 01HPC000000000 00H8255A400H01H02H03H
DADA SEGMENTBUFF DB 'This is a print program!''$'DATA ENDSCODE SEGMENT ASSUME CSCODE DSDATASTARTMOV AX DATA MOV DS AX MOV SIOFFSET BUFF
MOV AL 88H A0OUT 03H AL C00MOV AL 01HOUT 03HAL PC0WAIT IN AL 02H TEST AL 80H JNZ WAIT MOV ALSI CMP AL'$' JZ DONE OUT 00HAL A
MOV AL00H OUT 03H AL MOV AL 01H OUT 03HAL INC SI JMP WAITDONE MOV AL0DH OUT 00HAL MOV AL 00H OUT 03HAL MOV AL 01H OUT 03HAL
WAIT1 IN AL 02HTEST AL 80H PC71 JNZ WAIT 1 MOV AL0AH OUT 00HAL MOV AL 00H OUT 03HAL MOV AL 01H OUT 03HAL MOV AH4CH INT 21H CODE ENDSEND START
4 8255A1BUFF100CentronicsPC08255AA8255APC38259AIR3
8255A1010XXX0 PC0: 00000001 01HPC0 00000000 00HPC6: 00001101 0DH 8255AA8255A400H01H02H03H8259AICW208H A0BH2CH4
MAIN MOV AL0A0H OUT 03HAL 8255A MOV AL01H OUT 03HAL XOR AXAX MOV DSAX MOV AXOFFSET ROUTINTR MOV WORD PTR [002CH]AX MOV AXSEG ROUTINTR
MOV WORD PTR [002EH]AX MOV AL0DH OUT 03HAL 8255A A MOV DIOFFSET BUFF MOV CX99 MOV AL[DI] OUT 00HAL INC DI MOV AL00H OUT 03HAL
INC AL OUT 03HAL STI NEXT HLT LOOP NEXT HLT
ROUTINTRMOV AL[DI] OUT 00HAL A MOV AL00H OUT 03HAL INC AL MOV 03HAL INC DI IRET
18255A01228255AA2B
38255AA0B1C080H~83H48255AA0B0 8255AA1A0CPU8086A2A1A7A6A5A4A3=101008255A