Avoid FF

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Description

 

Message text:You must make sure that your application won't send any characters with ASCII code 255 (FF).

 


Details

 

This message is displayed when you have specified inband access method for the target DS. Inband access method is usually utilized when out-of-band access is not possible (i.e. because of restrictions on the network). To allow future programming of the target DS the Wizard will preserve inband access in the DS and this means that the Inband (IB) setting of the DS will be kept at 1 (enabled).

 

When the Inband (IB) setting of the DS is at 1 (enabled) the DS can accept commands sent by the remote host across the data connection and ASCII character with code 255 (FF Hex) is used as an "escape" character that signifies the beginning of a command and two FF characters need to be sent to transmit one data FF character (see inband programming for details).

 

If your application sends any FF characters the DS will interpret this as a beginning of an inband command, which is obviously a problem as all subsequent data will not be routed to the serial port of the DS. There are three solutions to this problem:

 

Find a way to program the DS using out-of-band access method. In this case the Wizard will disable inband commands on the DS side and all FF characters will be interpreted by the DS in a "normal" way.

 

Find a way to avoid sending ASCII characters with code FF between your application and the DS (your serial device).

 

Alter how your application handles all FF characters in a way compatible with the inband mode. This means that:

 

Whenever your application needs to send ASCII character FF it actually sends two consecutive FF characters;

 

Whenever your application receives two FF characters it interprets this as a single data character with code FF.