F.W. Bell 7030, Инструкция по эксплуатации

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F.W. BELL Model 7030 Gauss/Tesla Meter Instruction Manual
7-42 Section 7 – Remote Operation
EXAMPLE:
USING THE
EVENT, ENABLE,
AND CONDITION
REGISTERS
If you are overwhelmed by the use of the EVENT, CONDITION and
ENABLE registers, this example should help.
The goal is to get the attention of the computer when a reading is available
from Channel-2. This means we have to assert the SRQ interface line on
the GPIB bus, or set some status condition that can be read via the RS-232
port.
The “RQS” bit in the STATUS BYTE directly affects the SRQ interface line.
When it becomes “1” the line is asserted. “RQS” can be affected by six
conditions, four of which are controlled by event registers. In one of these,
the MEASUREMENT EVENT register, there is a bit called “RAV2”, which
sets to “1” when a reading is available from Channel-2. So, when “RAV2”
goes to “1” we want “RQS” to go to “1”.
1) To allow the “RAV2” event to reach the STATUS BYTE we must set the
corresponding bit in the MEASUREMENT ENABLE register. “RAV2” is
bit location D4. The decimal value that will set bit location D4 is 16.
The SCPI command is
:STATUS:MEASUREMENT:ENABLE 16
2) The “RAV2” event will now set the “MSB” (Measurement Summary Bit)
in the STATUS BYTE. But this will not set the “RQS” bit unless the
“MSB” event is enabled in the SRQ ENABLE register. “MSB” is bit
location D0. The decimal value that will set bit location D0 is 1. The
“common” command is
*SRE 1
Now as soon as a reading is available the “RQS” bit will set and the SRQ
interface line will be asserted. For GPIB users the system controller, not
knowing which instrument is requesting service, will sequentially read each
instrument’s serial poll register to determine who is asserting SRQ. For
RS-232 users there is no dedicated interface line that can be used to get
the attention of the computer. However, the STATUS BYTE can be
inspected from time to time to determine when an event has occurred.
This is done using the *STB? Command.
Normally the STATUS BYTE would be read first to determine the general
cause for the request, then the EVENT register would be read to determine
the exact nature of the request. The latter step is very important because
the act of reading the EVENT register is what clears the event. Simply
reading the STATUS BYTE or asking for Channel-2’s flux density reading
will not reset the “RAV2” bit. You must read the MEASUREMENT EVENT
register to reset “RAV2”. The SCPI command is
:STATUS:MEASUREMENT:EVENT?