PSC Scanners 4, Serial Communications

4User’s / Programming Guide

Serial Communications

The PSC scanner provides the user with two different serial commu-

nications options: Serial TTL and Serial RS232 communications.

Serial TTL is a serial communications interface that uses TTL/CMOS

voltage levels ranging from 0 to 5 volts. The user can select a nor-

mally high (default setting) or normally low (inverted) voltage levels.

Serial TTL communications mode uses different cables than those

used in keyboard wedge applications. To configure the PSC scanner

in a Serial TTL mode, the user must have the appropriate cable with

the correct signal pinouts in order to interface the scanner to the host

terminal. To program the PSC for Serial TTL communications, the

user must first identify the serial communications parameters sup-

ported by the host terminal. Typical parameters are the baud rate,

parity and number of bits in the data word. These parameters are dis-

cussed in the section on Serial Communication Parameters. The PSC

scanner has the added versatility to enable the user to select the qui-

escent voltage levels for interfacing with terminals that require

inverted signals.

The PSC scanner can also be used in an RS232 environment by con-

verting the serial TTL voltage levels to RS232 voltage levels. For this

installation, the user needs an optional cable, an adapter pod, and a

power supply.

When the PSC scanner is operated with the RS232 adapter pod, the

same serial communications parameters apply as those used in a

serial TTL environment. The only difference is that the RS232 adapter

pod inverts the polarity of all the signals passing through it. There-

fore, the user needs to program the scanner for serial communication,

normal polarity (symbol CA). RS232 levels are available only in full

continuous power mode.