TransCore encompass 4 - Data Inquiry Protocol; Basic Protocol and ECP Format

Data Inquiry Protocol
Data inquiry protocol is a basic protocol option that allows the host to control transmission of reader tag
data. The selection of data inquiry protocol aects data mode operation. As the Encompass 4 Reader
acquires tags, it buers them but does not transmit them. Instead, the host must poll the Encompass 4
Reader for each tag by sending an ASCII CRTL-E character (hexadecimal 05). The Encompass 4 Reader
transmits one message (tag ID or report data) for each CTRL-E it receives until the buer is empty.
Each tag request message sent by the host consists only of the CTRL-E character; no som or eom
characters are sent. Encompass 4 Reader data transmission (tag ID and report data) format is the same as
for basic protocol.
Selection of data inquiry protocol does not aect command mode operation.
Basic Protocol and ECP Format
Note: In the following text, the symbols < and > are used to represent required variable 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 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 Reader. The Encompass 4 Reader
updates its sequence number upon receipt of a valid host ACK. If an ACK is not
received, the Encompass 4 Reader retransmits the message. A reader transmission
sequence is not considered complete until the Encompass 4 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, or Error11 message; or a sign-on message. Auxiliary data may also be
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.
Chapter 6 Communications Protocols
TransCore Proprietary
6–73