User's Manual

PIN Pad 791 Programmer’s Manual (PCI POS-A) UDN PM0103-U Rev. 06
Section 4 – Message format 2015-04-20
Page26
Uniform Industrial Corp. Proprietary and Confidential Total 342 pages
Section 4 Message format
This chapter details the format of messages exchanged between the host and PIN Pad.
Notation Conventions
The following conventions are used to make the description of messages more readable:
Control Codes
Control codes (non-displayable codes) are represented by two to three capital letters enclosed in angled
brackets “<>“. This PIN Pad uses 12 control codes in total. Their actual code, when referenced, is
represented by two hex digits enclosed in angled brackets, <0F> for example. The following table lists
their usage and value in hex codes.
CODE HEX VALUE USAGE
STX 02 Denotes the beginning of a message frame
ETX 03 Denotes the ending of a message frame
EOT 04 Indicates communication session terminated
ACK 06 Acknowledge of message received
SI 0F Denotes the beginning of a message frame
SO 0E Denotes the ending of a message frame
NAK 15 Indicates invalid message received
SUB 1A Message parameter follows
FS 1C Field separator
GS 1D Message ID follows
DC1 11 Used for Z2 message, enable inverse mode.
DC2 12 Used for Z2 message, disable inverse mode.
[LRC]
Each message frame transmitted is followed by an LRC byte to detect communication error. This byte
should be regarded as part of the message frame but comes after the ending delimiter character. [LRC]
is used to represents this LRC byte in describing message frames.
LRC is calculated as an XORed value of every byte after start code in the message frame except itself,
that means from the next byte of <STX> or <SI> through the <ETX> or <SO> byte.
[item]
A descriptive item name enclosed in bracket denotes a string or data byte that has no fixed value.