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Programmers Manual
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with the P1 command. The SRQ mask works by monitoring the serial poll register, which
in turn monitors various conditions in the Meter.
The Serial Poll Register
The serial poll register is a binary-encoded register which contains eight bits, as
illustrated in Table 31. The controller can read the Meter serial poll register at any time
by taking a serial poll. Because serial poll register data is loaded directly onto the bus
(instead of being loaded into the output buffer first), reading the serial poll register leaves
data in the output buffer intact.
The eight bits of the serial poll register are described in Table 32. Note that the SRQ
mask uses bits 1 through 6 to set bit 7 (the RQS bit). When the RQS bit is set true, the
Meter sets the SRQ line true, which generates a service request. A bit is considered true
when it is set to 1.
For example, the serial poll register reads 00010000 (binary) when data is available. This
value is read in binary by the controller, which might numerically reformat the value
to 16 (decimal) or 10 (hexadecimal).
The serial poll register is cleared whenever the Meter receives a new input command string.
Table 31. Serial Poll Register
Bit
8 7 6 5 4 3 2 1
0 RQS Any Error
Data
Avaliable
0 0 0 Overrange
Decimal
Value
64 32 16 8 4 2 1
Table 32. Serial Poll Register Description
Bit Name Set Cleared
1 Overrange An overrange condition occurs Device command received, or Bus or
rear-panel trigger, or Output buffer is
read.
2 Not used Never Always
3 Not used Never Always
4 Not used Never Always
5 Data available Output buffer loaded with any
data (Readings, Error
messages, Get responses)
Device command received, or Bus or
rear-panel trigger, or Output buffer is
read.
6 Any Error An error condition occurs. At the
same time the output buffer is
loaded with an error message.
This sets bit 5.
Device command received or Output
buffer is read.
7 RQS Any SRQ mask-enabled bit is
set.
All SRQ mask-enabled bits are
cleared.
8 Not used Never Always
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