Specifications

Appendix B 557
GPIB Status Report System
General Model of Status Registers
B. GPIB Status Report System
Event Registers
The bits in an event register reflect corresponding the E4991A states such as event
occurrence. These bits are used to constantly monitor the E4991A state changes, and if a
certain condition defined for each bit is met, the corresponding bit is changed to 1. Note
that no GPIB command can change the status of event register bits.
The E4991A has the following types of event registers.
• Standard Event Status Register (For details, refer to Table B-2)
• Operation Status Event Register (For details, refer to Table B-3)
• Questionable Status Event Register (For details, refer to Table B-4)
• Questionable Status Hardware Event Register (For details, refer to Table B-5)
• Questionable Status Limit Event Register (For details, refer to Table B-6)
• Questionable Status Search Event Register (For details, refer to Table B-7)
Enable Registers
By setting the bit(s) in an enable register, the user can select bit(s) of an event register that
can set the summary bit in the Status Byte Register to 1 when an event has occurred. In
other words, enable register bits can function as mask bits, enabling the event register bits
corresponding to all of the enable register bits to be set to 1.
For example, you can specify that the summary bit in the Status Byte Register be set to 1
only when the bit in a certain event register is set to 1 by setting the corresponding enable
register bit to 1.