Filter
Top Products
Programming Guide – 30
error request error available error
• Bit 7 (self-test error) is set if a calibration error is detected after power-up or after the
self-test query (TST?) is executed. At all other times it is 0.
• Bit 6 (service request) is set when the interrupt request logic of the switch detects a reason
to generate a service request interrupt on the GPIB interface.
• Bit 5 (syntax error) is set when the parser detects a syntax error in a command mnemonic.
• Bit 4 (message available) is set when a message is available in the output buffer.
• Bit 2 (settled) is set when bit 2 in the condition register changes from 0 to 1.
• Bit 0 (parameter error) is set when a parameter value is out of the range of the SB switch.
The status register can be read with the status register query (STB?) or by serial polling the
GPIB interface. During power-up, the status register contains 0 and can only be read by serial
polling. After initial power-up, only the settled bit (bit 2) is set to 1. The clear status byte
command (CSB) and the clear device command (CLR) clear the status register. STB? also
clears the status register, but only if the service request bit (bit 6) is set to 1.
SRQ Mask Register
The SRQ mask register unmasks specific events in the status register that generate service
request interrupt on the GPIB interface (Table 11). The SRQ mask command (SRE) writes to
the SRQ mask register. When a bit in the SRQ mask register is set to 1, the interrupt logic of
the switch monitors the corresponding event bit in the status register. When a bit changes from
0 to 1, a service request interrupt is generated and bit 6 in the status register is set.
Table 11: SRQ Mask Register
SRQ Mask Register
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
self-test
error
n/a syntax
error
message
available
n/a settled n/a parameter
error
The SRQ mask register can unmask more than one event at a time. The first unmasked event
to change from 0 to 1 causes an interrupt. To acknowledge this interrupt, the GPIB interface
can be serial polled or the status register can be read with STB?. The first time the SB switch
is serial polled after an SRQ is generated, bit 6 is on. Subsequent serial polling returns a value
with bit 6 off. Similarly, STB? returns the status register with the SRQ bit set, but then the
switch logic automatically clears the register. As a result, subsequent STB? queries return 0.
The SRQ mask register is cleared by powering up the SB switch, by the clear device command
(CLR), or by the universal device clear command (DC1).
GPIB Programming Examples
This section provides programming samples for controlling the SB switch over the GPIB
interface. The samples were written in MS-DOS Qbasic and run on a personal computer