TransCore MPRX Series - Data Inquiry Protocol; Basic Protocol and ECP Format

MPRX User Guide
TransCore Proprietary
4–44
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 MPRX acquires tags, it buers
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 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. MPRX 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 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.