Quantum Data 802BT, 802R Sending commands and queries

102 Chapter 7 Using GPIB Interface

Sending commands and queries

The generator parses command lines one at a time. Command lines must be terminated

with a carriage return (<cr>).The generator immediately echoes each character as it is

received and places it in a command line buffer. This buffer currently has room for a total of

256 characters. If more than 256 characters are sent before sending a <cr>, then the

following response will be given:

Buffer overflow<cr><lf><cr><lf>R:\>

Upon receiving a carriage return, the generator immediately echoes the <cr> and follows it

with a line feed (<lf>). The generator then parses the command line and initiates whatever

processing is implied. The generator then responds with one of the following four

responses depending on the condition:

Command invalid<cr><lf><cr><lf>R:\>

Execution error: <nnnn><cr><lf><cr><lf>R:\>

R:\>

Where <cr> and <lf> are the carriage return and line feed characters, respectively.

Note: Handshaking routines should only look for > and not R:\>. In the future, the R:\ part

of the prompt may change (for example, may be expanded to indicate the current path).

Bench-top generators output the following prompt on their serial port after finishing the

power-on procedure.

R:\>

This feature allows ATE systems to know when the generator is ready.

You cans send multiple commands and queries per line by separating each command or

query with a semi-colon (;) character. For example:

HTOT 900; ALLU

The response to multiple queries will be a series of data elements separated by

semi-colons (;). For example, with the VGA_m3 format loaded, the following command

string will produce the response shown.

HRES?; VRES?; VTOT?

640;480;525

Normally, all of the commands on a command line associated with a single command

terminator are read as a single command message without regard for execution or

completion order. However, by inserting the *WAI command, you can force the generator