User guide

36
Remote Interface Reference
Command Handshaking
The Alarm Event register is queried using the
STATus:ALARm:EVENt?
command.
The Alarm Event
enable register
is cleared when:
The
STATus:ALARm:ENABle 0
command is executed.
The power is turned off and then back on, and the instrument was
configured for
*PSC 1
(power-on status clear). The enable register
settings are persistent if the Model 187 is configured for
*PSC 0
(no
status clear on power-on).
4.2.5 Command Handshaking
The Model 187 provides an internal command queue that can store up to 4
commands or queries. However, it is possible that the host computer can
overwhelm the command queue by sending commands faster than the
Model 187 can execute. If the Model 187 cannot process a command due to
a full command queue, the command is ignored and the
-303,"Input
overflow"
error is reported.
Handshaking is generally not a concern unless more than 4
commands
are
sent sequentially. If a
query
is sent, the user will normally wait for return
data for the queries before proceeding to send the next query or command.
In the case of sending numerous
commands
in sequence, there are two
methods available to help prevent command queue overflows which are
discussed below.
Table 4-3. Bit definitions for the Alarm Condition and Event registers.
Bit Number
Decimal
Value Definition
0
HI Alarm
1
“HI” alarm condition or event.
1
A Alarm
2
“A” alarm condition or event.
2
B Alarm
4
“B” alarm condition or event.
3
LO Alarm
8
“LO” alarm condition or event.
4
RATE Alarm
16
“RATE” alarm condition or event.
5
Over/Under Flow
32
The reference sensors are either
both submerged or exposed.
6
Maximum Dielectric
Exceeded
64
The maximum allowable dielectric
has been exceeded. The maximum
allowable value is recorded on the
first page of this manual.
7
Not Used 128 Always “0”.