9560 Transaction Manager User's Manual - Intermec

9560 Transaction Manager User’s Manual
Data Format Requirements
5-10
Regardless of the protocol you selected, the host and the reader must format
the data before transmitting it. Each transmission includes a start character, the
data block, and an end character. The SOM (start of message) character and the
EOM (end of message) character are determined by the protocol. The data
block may include preambles, data, and a postamble.
The following figure shows the data format parameters. The Intermec Data
Communications Reference Manual describes these parameters in detail.
SOM Preamble Record Postamble EOM(s)
Data Block
SOM Character (Start of Message)
The SOM character precedes the data and indicates the beginning of a data
block. The SOM character is a protocol character and is not part of the data
format.
Preambles and Postambles
The preamble is a field of data sent before record data and a postamble is sent
after record data. Preambles and postambles are typically used to tag
transactions for rapid processing by the host computer. They are also used to
expand the data field (record) length. The reader has two preambles,
Preamble A and Preamble B, and one postamble, Postamble C.
If you select “Preamble A Required” in Configuration mode, you must also
define Preamble A. For preamble commands, see Chapter 8, “Data Entry
Commands.” Your preamble definition is erased if you reset the reader to the
default settings. You will need to re-enter the preamble to use it again.
When the reader transmits a message block, the presentation control first
checks to see if the preamble or postamble functions are enabled and defined.
If they are, then the transmitted data has the following format:
message block
The message may consist of a single record or multiple records. If a file is being
transmitted with multiple records per message block, the message block has
the following format:
record record record last record