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5.4.3
Serial data format
The format of 10-bit or 11-bit serial data, given in Figure 5.12, consists of a start bit, data bits, a parity bit, and stop
bits. A bit is in the mark state when not being transmitted. Data bits start with the least significant bit (LSB). For
example, the character "K" (hexadecimal 4B) is transmitted as shown in Figure 5.12 (7 data bits, even parity).
High, +, or Space
Low, –, or Mark
5.4.4
Cable connection diagrams
The connector at the printer side is a 9-pin type. The connector at the computer side is a 9-pin type or a 25-pin type.
Figure 5.13a Example of RS-232C cable wiring (25-pin connector at computer side)
Start
bit
1
2
1
1
0
Figure 5.12 RS-232C data format
Computer (DTE)
CD
(pin 8)
RD
(pin 3)
TD
(pin 2)
DTR
(pin 20)
SG
(pin 7)
DSR
(pin 6)
RTS
(pin 4)
CTS
(pin 5)
RI
(pin 22)
FG
(pin 1)
Shell
Data bits
4
3
5
6
1
0
0
0
Printer (DTE)
RTS
TD
RD
DSR
SG
DTR
#
DTR
#
Shell
# Open wire
Parity
Stop
bit
bit(s)
7
1
1
(1)
0
(pin 1)
(pin 2)
(pin 3)
(pin 4)
(pin 5)
(pin 6)
(pin 7)
(pin 8)
(pin 9)
5-15
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