•
A command is transmitted in a message, which can contain more than one command. For
example,
SWITCH 1 1 3;SWNUM? <CR> <LF>
contains two commands.
•
All GPIB messages must end with the terminating sequence <CR> <LF>.
•
All RS232C commands must be terminated with a single <CR> character.
•
The input buffer of the SCG unit can hold 100 characters. If the buffer is full, the unit holds
the handshaking line on the GPIB interface until space is available. Similarly, over the
RS232C interface, the SCG unit sets the Clear To Send
line
low. Any characters received
after the line goes low are ignored.
•
Commands are executed as they are parsed; consequently, a command can be executed
before the entire message in which it is contained is received.
•
The SCG unit delays accepting new characters sent over the GPIB interface while the
switch mechanism is moving, but no data are lost. The SCG unit is always ready to accept
characters over the RS232C interface.
•
A query command is used to extract status information from the SCG unit. For example,
SRE? <CR> <LF>
returns the contents of the status register (see the
•
Multiple-command messages can contain only one query command. A query must be the
last command in the message, for example,
SWITCH 1 1 1; XDRS? <CR> <LF>
.
Operation Commands
RESET Reset
Returns the SCG unit to the power-up state, for example, channel 0, relay drivers off. All motors
and non-latching relay switches are returned to the reset position. The state of the latching
switches is not modified.
SRE I
Clear Status Byte
Writes a decimal number to the SRQ mask register (see the
section). Setting a bit to 1 generates an SRQ interrupt when the
corresponding bit in the status register changes from 0 to 1.
CSB
Clear Status Byte
Resets the status register.
CLR Clear
Device
Clears the SRQ mask register.
Programming Guide –
26
