TransCore 05716 Manuel D’Utilisation

number, and advances pointers to the next message in the MPRR’s message queue to 
prepare for sending the next message.

The host computer may issue command #01 Switch to Command Mode while in data 
mode.

The basic protocol format is as follows:

<som><cmd><eom>

The ECP format is as follows:

<som><seq><cmd><crc><eom>

where

<som>

Start-of-message (ASCII # character)

<seq>

Sequence number generated by the host computer separately 
from that appearing in data messages transmitted by the MPRR 

<cmd>

Switch to command mode (ASCII characters 01)

<crc>

CRC value for the message

<eom>

End-of-message character (ASCII CR)

The host computer initiates synchronous communications between the MPRR and the 
host. The host begins a sequence by issuing a command; the MPRR responds accord-
ingly.

The basic protocol format is as follows:

<som><cmd>[<data>]<eom>

The ECP format is as follows:

<som><seq><cmd>[<data>]<crc><eom>

where

<som>

Start-of-message (ASCII # character)

<seq>

Sequence number (ASCII hex digit) that represents an odd 
number in the range 0–9, A–F (1, 3, 5, 7, 9, B, D, F). The host 
should use odd sequence numbers in its command since the 
MPRR uses even sequence numbers in its transmissions. This 
method eliminates the possibility of a synchronous host 
command and an asynchronous reader transmission having the 
same sequence number.