TransCore MPRX, System Manual

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System Guide
TransCore Proprietary 6–4
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 affects data mode operation. As
MPRX acquires tags, it buffers them but does not transmit them. Instead, the host must
poll MPRX for each tag by sending a CTRL-E character (hex 5 digit). MPRX transmits one
message (tag ID or report data) for each CTRL-E it receives until the buffer is empty.
Each tag request message sent by the host consists only of the CTRL-E character; no som
or eom characters are sent. MPRX data transmission (tag ID and report data) format is the
same as for basic protocol.
Selection of data inquiry protocol does not affect 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 MPRX maintains the number.
The host must acknowledge reader transmissions by sending an
ACK
message with the same sequence number received from the MPRX. The
MPRX updates its sequence number upon receipt of a valid host
ACK
.
If an
ACK
is not received, the MPRX retransmits the message. A reader
transmission sequence is not considered complete until the MPRX
receives an
ACK
and updates its sequence number.
<data>
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.