??????

1
???????

• ?????????????????????????????????
• ?????????????,???????,?????????????,
• ??????????????????????????
• ?????????,????????????????????????

2
????--????
???????lt- -gt????????,??????????? (UARTUnivers
al Asynchronous Receiver and Transmitter), ??????
Intel 8250/8251,16550?
3
(No Transcript)
4
???
??? (bps) 1 ???????(??) 2 ???????(??)
110 5000 3000
300 5000 3000
1200 3000 3000
2400 1000 500
4800 1000 250
9600 250 250
5
???????

• ???1??2?
• ???1??1.5??2?

6
???

• .????????????
• ?????????
• .?????
•   ?????????RTS/CTS(????/????)????DTR/DSR(??????/??
  ????)???
• .?????
• ????XON/XOFF?????????

7
????

• ??????????(???????????)?,1??????,?
• 1 0110,0101
• 0 0110,0001
• ??????????(???????????)?,1??????,?
• 1 0100,0101
• 0 0100,0001

8
(No Transcript)
9
1.????

• EIA-RS-232C????????????????????????
• ?TxD?RxD???1(MARK) -3V-15V
•               ??0(SPACE)315V
• ?RTS?CTS?DSR?DTR?DCD?????
• ????(??,ON??,???)3V15V
• ????(??,OFF??,???) -3V-15V

10
TTL??RS232????
11
????????
12
??????????
9???(DB9) 25???(DB25)
?? ???? ?? ?? ???? ??
1 ?????? DCD 8 ?????? DCD
2 ???? RXD 3 ???? RXD
3 ???? TXD 2 ???? TXD
4 ?????? DTR 20 ?????? DTR
5 ??? GND 7 ??? GND
6 ??????? DSR 6 ????? DSR
7 ???? RTS 4 ???? RTS
8 ???? CTS 5 ???? CTS
9 ???? DELL 22 ???? DELL
13
2?RS-232C?????DSR DTR

• RS-232C??????25??,4?????11?????3?????7????????,???
  ??9?,???
• (1)???????
• ???????(Data set ready-DSR)???(ON)??,???????????
  ?????
• ???????(Data set ready-DTR)???(ON)??,???????????
  
• ????????????,????????????????????,?????????,??????
  ???????????,????????????????????

14
RS-232C?????RTS CTS

• ????(Request to send-RTS)????DTE??DCE????,??????
  ????,??????(ON??),?MODEM??????????MODEM??????????
• ????(Clear to send-CTS)????DCE?????DTE?????,????
  ????RTS???????MODEM?????????????,??????,??????,???
  ?????????TxD?????
• ??RTS/CTS??????????????MODEM??????????????????????
  ??????????????????????????,???????,????RTS/CTS????
  ,?????

15
RS-232C?????DCD RI

• ???????(Received Line detection-RLSD)????DCE????
  ???,??DTE???????????MODEM??????????(??)?MODEM?????
  ???,?RLSD????,????????,???MODEM???????????????????
  ,??????RxD????????????????(Data Carrier
  dectection-DCD)??
• ????(Ringing-RI)?MODEM???????????????,??????(ON?
  ?),????,?????

16
RS-232C????? ---TxD RxD

• (2)????????
• ????(Transmitted data-TxD)??TxD??????????MODEM,(
  DTE?DCE)?
• ????(Received data-RxD)??RxD??????MODEM???????,(
  DCE?DTE)?
• (3)??
• ????SG?PG??????????,????

17
????
A
B
18

NULL MORDEM ?????
2
1
2
4
3
4
19
NULL MORDEM ?????
5
20
???????????
????
????
????
21
??????

• ?????????????
• ????????????????????
• ??????????????????????????
• ????????????????,?????????,????????
• ???????,???????,????????(????)????

22
????

• ??,??????????????????,????????36?????25?D????????
  ,??8??????????????,????????????,??????????????,??
  ????,??????,?????
• ??????????4??8???8??EPP?ECP,???PC???4??8????,????
  Intel386?????????EPP?,????IEEE1284??????????ECP???
  
• ?????4??8???8?4????????4???,?????8???8??????????
  ?8????8?????
• EPP?(?????)?Intel?????,??8???????,????????????,??
  ???LAN??????????CDROM ?????
• ECP?(?????)?Microsoft?HP????,????????????????????
  ?,???????????DMA(????? ??)?

23
?????????????

• ????????????,???????A?????B,??????
• ???????,?????A??B,???B?A,??????????????,????????
• ???????,?????A?B?B?A???????,???????

24
??????
--------gt lt--------gt --------gt
A-------B A--------B A-------B
lt-----------------
?? ??? ???
????????????? ???????????,?????????????? ?????????
??????,???????????????????,
??????
25
??????

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