23
movement command is received. Transmission from the host must then pause. DTR will later go true
(positive voltage) or a DC1 (Xmit on) will be transmitted when space becomes available and host
transmission may resume. DTR is equivalent to most operating systems’ hardware protocol.
Under the DTR and XON/XOF protocols ENQ will still generate the normal status response but it is not
necessary to transmit ENQs in order to cause command execution. However, if ENQ and DC1 are never
issued and status responses are never examined by the host, it is difficult to use the keypad for system input.
3.13.3 Interface Signals
The interface provides for RS-232 communication. All signals are available on a 25 pin male connector
equivalent to Cinch DB-25P.
If the Dual Port option is installed there will be two identical 25 pin male
connectors. All connectors have 4-40 threaded inserts for positive mating. Pin assignments are as follows:
Pin Signal
Description
1
Protective ground
Attached to printer frame.
2
Transmit Data (TD)
From printer, transmits printer status.
3
Receive Data (RD)
To printer, receives data & commands.
4
Request To Send (RTS)
From printer, indicates printer is ready to transmit
5
Clear To send (CTS)
To printer, enables status transmission.
6
Data Set Ready (DSR)
To printer, enables printer to receive data and commands.
7
Signal ground
Attached to printer logic ground.
20 Data Terminal Ready (DTR)
From printer, indicates printer is ready to communicate. Also
indicates input buffer available if DTR protocol is selected.
Note that regardless which interface is used DSR must be active for the printer to receive commands and
CTS must also be active for the printer to transmit status. If no connection is made to these signals, they are
biased active in the printer.
The following cable connection will work correctly in most applications using PC type 25 or 9 pin serial ports.
A shielded cable with only one end of the shield connected to a metal connector cover or pin 1 of a 25 pin
connector is recommended to increase immunity to static discharges and other electrical noise.
Manufacturer’s part number is 72118-1 for a 9 pin PC cable.
Printer Pin
PC-25 Pin
PC-9 Pin
Signal
3
2
3
Data to Printer
2
3
2
Data from Printer
20
5
8
DTR to PC CTS
-
6,20
4,6
PC DTR to PC DSR
7
7
5
Signal Ground
Some applications (Online, Microbilt, Bisys, Intrieve) check DSR rather than CTS for printer status. Use the
following cable with such software. Manufacturer’s part numbers are 72100-1 for a 9 pin PC cable and
72098-1 for a 25 pin PC cable.
Printer Pin
PC-25 Pin
PC-9 Pin
Signal
3
2
3
Data to Printer
2
3
2
Data from Printer
20
5,6
6,8
DTR to PC CTS & DSR
7
7
5
Signal Ground