User Manual LW120
user can read from and write to an Enable Register. Querying an
Enable Register will not clear it. The *CLS command does not clear
Enable Registers but it does clear bits in the event registers. To
enable bits in an enable register, write a decimal value that
corresponds to the binary-weighted sum of the bits required to enable
in the register.
The Status Byte
Register (STB)
The Status Byte summary register contains conditions from the other
registers. Query data waiting in the generator's output buffer is
immediately reported through the Message Available bit (bit 4). Bits in
the summary register are not latched. Clearing an event register will
clear the corresponding bits in the Status Byte summary register.
Description of the various bits within the Status Byte summary register
is given in the following:
Bit 0
- Decimal value 1. Not used, always set to 0.
Bit 1
- Decimal value 2. Not used, always set to 0.
Bit 2
- Decimal value 4. Not used, always set to 0.
Bit 3
- Decimal value 8. Not used, always set to 0.
Bit 4
- Decimal value 16. Message Available Queue Summary
Message (MAV). The state of this bit indicates whether or not the
output queue is empty. The MAV summary message is true when
the output queue is not empty. This message is used to
synchronize information exchange with the controller. The
controller can, for example, send a query command to the device
and then wait for MAV to become true. If an application program
begins a read operation of the output queue without first checking
for MAV, all system bus activity is held up until the device
responds.
Bit 5
- Decimal value 32. Standard Event Status Bit (ESB)
Summary Message. This bit indicates whether or not one or more
of the enabled ESB events have occurred since the last reading or
clearing of the Standard Event Status Register.
Bit 6
- Decimal value 64. Master Summary Status (MSS)/Request
Service (RQS) Bit. This bit indicates if the device has at least one
condition to request service. The MSS bit is not part of the IEEE-
STD-488.1 status byte and will not be sent in response to a serial
poll. However, the RQS bit, if set, will be sent in response to a
serial poll.
Bit 7 - Decimal value 128. Not used, always set to 0.
Remote Programming Reference 4-62