Tektronix 071-0855-05 user manual Hex Block Format

Reference: Remote Commands ~ Syntax

Block Format

IEEE-488 block format is a means of encoding arbitrary binary data, including characters that aren’t valid in text strings, for transmission over a GPIB link. The format is most easily explained with an example.

This is a block containing 16 bytes of data:

#216abcdeFGHIJklmnop

where:

‘#’ denotes the start of a block

‘2’ is the number of digits that follow, to represent the byte count in the block ‘16’ is the number (represented by two decimal digits) of data bytes ‘abcdeFGHIJklmnop’ is the 16 data bytes in this example

The OTS9100 uses blocks in commands and queries for overhead data and section trace sequences; the descriptions of these commands include the number of bytes expected or sent.

Hex Block Format

The GPIB can transmit eight-bit binary data without problems. But the OTS9100 can also be controlled over RS-232 serial links and Telnet protocol over network links. These may not be able to send eight-bit data or ASCII control characters. For this reason, the OTS9100 remote command system implements an alternative block format called hex block format in which each byte of binary data is sent as two hex digits using the characters 0 to 9 and A to F.

Blocks in hex format thus consist of twice many characters as the corresponding blocks in binary format.

The block in the example above would be, in hex format,

#2326162636465464748494A6B6C6D6E6F70

where

‘#232’ is the prefix for a 32-character block

‘61’ is the hexadecimal representation of “a,” the first character in the block ‘62’ is the hexadecimal representation of “b,” and so on.

Note that the block’s count of data bytes is doubled, representing twice as much data as in the binary- format block.

The OTS9100 system must be explicitly set to transmit or receive blocks in binary or hex block format. See the description of the command.

OTS9100 User Manual 3-7