TransCore 0596465PT15 Manuel D’Utilisation

If the Encompass 4H Reader detects an incorrect CRC value in a host command mes-
sage, it discards the received message. No response is sent. If it receives an incorrect 
CRC value in an ACK message, it responds as if a NAK had been received, and it 
retransmits the data.

If the Encompass 4H Reader receives an illegal command, it returns its standard 
Error

 message.

If the Encompass 4H Reader transmits an asynchronous message and the host does not 
send an ACK

before the ECP timeout occurs, the Encompass 4H Reader retransmits 

the message.

If the Encompass 4H Reader receives a 

but does not receive a matching 

before the ECP timeout occurs, it discards the incomplete message and resets 

its receiver.

If the Encompass 4H Reader transmits asynchronous data at the same time that the 
host sends a command, the Encompass 4H Reader gives priority to receiving the com-
mand. It processes the command and sends a message before it retransmits the asyn-
chronous data.

The host computer addresses the following failure conditions.

If the host detects an illegal or wrong sequence number in a reader response, it retrans-
mits the command with the same sequence number. If the host detects an illegal 
sequence number in an asynchronous reader transmission, it sends a NAK

message.

If the host detects an incorrect CRC value in a reader message, it retransmits the com-
mand with the same sequence number. If the host detects an incorrect CRC value in an 
asynchronous reader transmission, it transmits a NAK

message.

If the Encompass 4H Reader does not respond to a host command within a specified 
interval, the host software retransmits the command with the same sequence number.