Programming Guide

CHUMP Reference Guide
30
Ro
Name
Read digital input and output
Description
SAMSys readers have four optically isolated input lines and four
transistor buffered output lines. The lines are unidirectional.
Refer to the reader owner’s manual for deatiled information on
the digital input/output lines.
This command reads the digital input/output port on the reader
and returns a 2-digit HEX value (d:xx). The lower digit
(secondx) represents the last value written to the four digital
output lines. The higher digit represents the current value of the
four digital input lines.
Current flow through an input produces a logical 0 at the
microprocessor which produces a logical 0 in the Ro reply. If the
inputs are all open, the Ro reply is “ff”. On powerup, the output
lines are all set to 1. As a result, the Ro command returns all 1s
prior to the first Wo command.
Type
Reader management command with reply
Format
}Ro;79<CRLF>
}Ro!<CRLF>
Return Message
{Ro,d:<data>;<FCS><CRLF>