1.nterface connector terminal assignments and signal functions
Pin number Signal name Signal Source Description
2 TXD Printer When using XON/XOFF
handshake protocol, printer
transmits control code XON/XOFF
3 RXD Host Printer receives data from host
4 RTS Printer Indicates printer current status,
whether the printer is Busy or
Ready to receive data
7 GND Signal ground
20 DTR Printer Same as RTS (pin 4)
1. Data transmission: Parallel
2. Synchronization: Externally supplied nStrobe signals
3. Handshaking: nAck and Busy signals
4. Signal levels: TTL compatible
5. Data word length: 8 bits
6. Connector (printer side): 36 pins Centronics connector
b. IEEE 1284 Bidirectional Parallel Interface(Parallel Interface
Specifications)
b.1) Parallel Specifications
-21-
-20-
b.2) Parallel Interface Pin Assignments for Each Mode
Pin Mode Source
1 /STB Host The computer presents the data on the
data lines, and pulses STB
2 DATA0 Host Indicates the 1st data bit through 8th
data bit
3 DATA1 Host
4 DATA2 Host
5 DATA3 Host
6 DATA4 Host
7 DATA5 Host
8 DATA6 Host
9 DATA7 Host
10 nAck Printer Printer acknowledge signal which
indicates that printer has received
previous data bit
11 BUSY Printer Printer is busy and cannot receive
data
12 GND Ground
13 Select Printer High electric potential
14 15 NC No Connect
16 17 GND Ground
18 Logic-H Printer High electric potential
19 30 GND Ground
31 NC No Connect
32 Nerror Printer Printer Error Signal
(nFault)
33 GND Ground
34 36 NC No Connect
