Quantum Data 801GC, 801GF, 801GX manual Controlling via the IEEE-488 Port, Input Buffer

Controlling via the IEEE-488 Port

You do not need to do anything special on the 801G* to use it’s IEEE-488 port. The default settings are for the 801G* to be a talker/listener with an ad- dress of 15.

All of the commands and queries shown at the end of this chapter can be used over the port. This sec- tion covers how the commands should be sent over the GPIB bus. Information on additional commands that can only be sent through the GPIB port is also included in this section.

Input Buffer

Commands are sent to the 801G* in “program mes- sages.” A program message consists of one or more commands separated by a semicolon (;) followed by a program message terminator. A program message terminator is defined as the NL character (ASCII 10), or EOI sent with the last byte of the program message. The 801G* will not parse any commands received until a program message terminator is re- ceived. All commands are executed sequentially, that is, when a command is parsed it is allowed to finish execution before the next command is parsed.

Since some commands may take longer to execute, the 801G* has an input buffer. This input buffer is 255 characters long and can be written to by the host controller while the 801G* is busy executing or parsing previous messages. If the input buffer be- comes full, the 801G* will hold off the controller until there is room in the buffer. For this reason, a program message cannot be longer than 255 charac- ters including terminator.

6-62 Chapter 6: Programming Model 801GC, 801GF & 801GX¥Rev. A