Citizen Systems Citizen CLP 621 CLP-621 - Manual (Page 54)

Appendixes
54
Parallel Interface
Specifications
Transmission mode 8-bit parallel data
Receive buffer size 16kB
Transmission modes Compatible mode
It is an asynchronous forward direction of the byte width
(from host to printer) channel, and the interface line of
the data is operated in accordance with signal line
definitions of Centronics.
NIBBLE mode
Nibble mode is asynchronous reverse channel
communication with data transmission controlled by the
host computer. In reverse channel transmission, the data is
nibble transmitted in two parts using four status lines (Fault,
Select, PE, and Busy). And nibble mode can be used along
with compatible mode to send data in two directions.
ECP mode
ECP mode permits bi-directional asynchronous data
transmission, and thanks to its interlock handshake, it does
not require the timing necessary with compatible mode.
Signal level IEEE1284 standard
Pin No. Signal name I/O Function
1 *STROBE Input Strobe signal to read in 8-bit data
2-9 DATA1-8 Input 8-bit parallel signal
10 *ACKNLG Output 8-bit data request signal
11 BUSY Output Signal specifying printer busy
12 PERROR Output Signal specifying media out
13SELECT Output Signal specifying if the printer is on-line (printing
enabled) or off-line (pausing)
14 AUTOFD Input Invalid (ignored)
15 NC --- Not used
16 GND --- Signal ground
17 FGND --- Frame ground
18 P.L.H Output Peripheral logic high (pull up to +5V at 1k Ω)
19-30 GND --- Ground for twisted pair return
31 *INIT Input Printer reset
32 *FAULT Output Signal specifying printer error
33 -35 NC --- Not used
36 SELECTIN Input Invalid (ignored)
Signal line and pin assignment table
Interfaces