The communication buffer size is 13 bytes maximum for Transmitter and receiver (Half duplex). The BCS is transmitted as ASCII Hex, the least significant digit transmitted first.ĪSCII characters 02h (STX) and 03h (ETX) are used as communication block delimeters. Note - Transmission Block Checksum: It is the XORSUM of all bytes starting and including STX and ending with and including the last data character. Sequence No= 1 byte (0 or 1), Always 0 for single transmission command types or toggled for successive frames of the same command type, to enable detection of retransmissions.ĭata= 0 - 1000 bytes, The data associated with the command typeīCS2 = 1 byte, Least significant digit of block check character īCS1 = 1 byte, Most significant digit of block check character ĮTX = 1 byte (Hex code: 03h), End of transmission marker. Specifies the command to be executed by the slave immediately or the data structure that follows in the data field. STX = 1 byte (Hex code: 02h), Start of transmission markerĪddress = 1 byte (A - Z), Address of the slave to which the message is relevantĬommand = 1 byte (Hex code: 30h - 5Ah), Command type. STX | Address | Command | Sequence No | Data | BCS 2 | BCS 1 | ETX | The details are as follows:Īll communication is performed in a standard message format as shown below, The problem is that the device is utilising a special kind of protocol and I am not sure how can I implement it in Visual Basic. I need to make a software that communicates with an external digital device. General Information - Binary Synchronous Communications, third edition, October 1970 (PDF). General Information - Binary Synchronous Communications, first edition (PDF). 'Bisync DLC Character Codes in Communications Trace on OS/400 or i5/OS System'.

'What is Bisync? A Short History Lesson'.

Detailed discussion of Bisync link control by Charles A Wilde (new link).

General Information - Binary Synchronous Communications (PDF). 'Binary Synchronous Communications (BSC)'. 'Binary Synchronous and Asynchronous Communications (Bisync/Async)'. 'Terrestrial to Satellite Switching Creates Options'.

IBM 3270 Display Terminal Subsystem control units.

A large number of devices use the Bisync protocol, some of these are:

Serial protocol stx etx