TransCore MPRX, System Manual

Page: 79 / 208

MPRX
TransCore Proprietary 6–9
Host Command Transmissions
Basic protocol host transmission
#647XXX<eom>
Reader response
#Done<eom> or #Error<eom>
#Error<eom>
is returned if the host transmission is not a legal command with legal data.
ECP host transmission
#7647XXX<crc><eom>
where
#
Start-of-message character
7
Message sequence number
647XXX Select RF Operating Frequency
command where 647XXX is the
command and XXX is a hexadecimal value from 000 to 118. In this example,
XXX sets the RF frequency to 903 MHz.
<crc>
CRC value for the message
<eom>
End-of-message character
Done
Command has been invoked by the MPRX
Reader response
#7Done<crc><eom> or #7Error<eom>
For some commands, the MPRX responds with data that relates to the command, such
as T0F 0, to indicate the mode enabled for a #570 Display Operating Mode Status
command.
#7Error<eom>
will be returned if host transmission is not a legal command with legal
data.
Timing and Synchronization
The ECP is largely independent of baud rate. The timeout delays previously described are
a function of baud rate.
The MPRX supports an ECP timeout, which applies equally to both transmit and receive.
The receiver’s minimum timeout delay equals the time to transmit/receive the longest
anticipated message at the current baud rate setting. Additional margin should be included
for idle periods between characters; for example, processing overhead, if any. The timeout
delay period can be expressed as follows:
Τ
rec
(ms) = L x [ Τ
char
+ Τ
idle
]