TransCore 05531 User Manual
Communications Protocols
6-5
mitted before receipt of the eom character. In this case, the Encompass 4/4800 Multi-
protocol Reader will issue an Error message, and the host computer will issue a
negative acknowledgment message.
protocol Reader will issue an Error message, and the host computer will issue a
negative acknowledgment message.
Basic Protocol and ECP Format
Note: In the following text, the symbols < and > are used to represent required vari-
able message data, and the symbols [and] are used to represent optional data. These
symbols are not part of the message syntax.
able message data, and the symbols [and] are used to represent optional data. These
symbols are not part of the message syntax.
Reader Transmissions
The basic protocol format and the data inquiry protocol format are as follows:
<som><data><eom>
The ECP format is as follows:
<som><seq><data><crc><eom>
where
<som>
Start-of-message (ASCII # character)
<seq>
Sequence number (ASCII hex) that represents an even number in
the range 0–9, A–F (0, 2, 4, 6, 8, A, C, E). The Encompass 4/4800
Multiprotocol Reader maintains the number. The host must
acknowledge reader transmissions by sending an ACK message
with the same sequence number received from the Encompass 4/
4800 Multiprotocol Reader. The Encompass 4/4800
Multiprotocol Reader updates its sequence number upon receipt
of a valid host ACK. If an ACK is not received, the Encompass 4/
4800 Multiprotocol Reader retransmits the message. A reader
transmission sequence is not considered complete until the
Encompass 4/4800 Multiprotocol Reader receives an ACK and
updates its sequence number.
the range 0–9, A–F (0, 2, 4, 6, 8, A, C, E). The Encompass 4/4800
Multiprotocol Reader maintains the number. The host must
acknowledge reader transmissions by sending an ACK message
with the same sequence number received from the Encompass 4/
4800 Multiprotocol Reader. The Encompass 4/4800
Multiprotocol Reader updates its sequence number upon receipt
of a valid host ACK. If an ACK is not received, the Encompass 4/
4800 Multiprotocol Reader retransmits the message. A reader
transmission sequence is not considered complete until the
Encompass 4/4800 Multiprotocol Reader receives an ACK and
updates its sequence number.
<data>
An ASCII string up to 72 characters long. This string may contain
tag data, a presence without tag report; an input status change
report; an Error06, Error07, Error08,
tag data, a presence without tag report; an input status change
report; an Error06, Error07, Error08,
or
Error11
message; or a sign-on message. Auxiliary data may also be
included.
included.
<crc>
Field containing four ASCII digits that represent the 16-bit CRC
value calculated on the message. The CRC value is calculated on
bytes between the som character and the first <crc> byte.
value calculated on the message. The CRC value is calculated on
bytes between the som character and the first <crc> byte.
When the host receives a properly framed message, it can
calculate a 16-bit CRC value. The calculation is applied to the
calculate a 16-bit CRC value. The calculation is applied to the