Fluke 8846A - External Triggering; Service Requests (IEEE 488 Only) and Status Registers

8845A/8846A
Programmers Manual
22
External Triggering
There are three methods of triggering the Meter externally:
• A trigger signal applied to the external trigger jack on the Meter’s rear panel.
When the Meter’s trigger source is set to external and the Meter is in a wait-for-
trigger state, a negative-going signal on the external trigger jack will trigger a
measurement cycle.
• IEEE 488.1 GET command (IEEE Interface only)
• *TRG command
When the Meter’s trigger source is set to BUS and the Meter is in a wait-for-trigger
state, either a *TRG or bus GET command will trigger the Meter to take
measurements.
Service Requests (IEEE 488 Only) and Status Registers
Service requests let an instrument on the IEEE 488 bus get the attention of the host. Service
requests are sent over the service request (SRQ) bus line.
If more than one instrument on the bus is capable of sending service requests, the host can
determine which instrument made the request by taking a serial poll. Each instrument on the
bus responds to the poll by sending the contents of its Status Byte Register. If an instrument
on the bus has made a service request, the request service bit (RQS, bit 6) of its Status Byte
Register will be set to 1, identifying it as an instrument that requested service.
The contents of the Status Byte Register (STB) is determined by the Service Request
Enable Register (SRE), Standard Event Status Register (ESR), Standard Event Status
Enable Register (ESE), Questionable Data Event Register, Questionable Data Enable
Register, and the output buffer. These status registers are discussed below, and
summarized in Table 4. Figure 3 shows the relationship of these registers.
Table 4. Status Register Summary
Register Read Command Write Command Enable Register
Status Byte Resister *STB? None SRE
Status Byte Enable Register *SRE? *SRE None
Standard Event Register *ESR? None ESE
Standard Event Enable
Register
*ESE? *ESE None
Questionable Data
Event Register
STAT:QUES:EVEN? None Questionable Data
Enable Register
Questionable Data
Enable Register
STAT:QUES:ENAB? STAT:QUES:ENAB
<value>
None