PC串行口引脚定义图
PC/AT 机上的串行口是 9 针公插座，引脚定义为：
Pin
Name
Dir
DescripTIon
1
CD
Carrier Detect
2
RXD
Receive Data
3
TXD
Transmit Data
4
DTR
Data Terminal Ready
5
GND
System Ground
6
DSR
Data Set Ready
7
RTS
Request to Send
8
CTS
Clear to Send
9
RI
Ring Indicator
PC/XT 机上的串行口是 25 针公插座，引脚定义为：
Pin
Name
Dir
DescripTIon
1
SHIELD
-
Shield Ground
2
TXD
Transmit Data
3
RXD
Receive Data
4
RTS
Request to Send
5
CTS
Clear to Send
6
DSR
Data Set Ready
7
GND
-
System Ground
8
CD
Carrier Detect
9
n/c
-
10
n/c
-
11
n/c
-
12
n/c
-
13
n/c
-
14
n/c
-
15
n/c
-
16
n/c
-
17
n/c
-
18
n/c
-
19
n/c
-
20
DTR
Data Terminal Ready
21
n/c
-
22
RI
Ring Indicator
23
n/c
-
24
n/c
-
25
n/c
-
