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Operating the Meter Using the Computer Interface
Service Requests (IEEE-488 Only and Status Registers
5
5-17
Table 5-6. Description of Bits in ESR and ESE
Bit No. Name True (Set to 1) Conditions
0
1
2
3
4
5
6
7
Operation Complete (OPC).
Not used.
Query Error (QYE).
Device-Dependent Error (DDE)
Execution Error (EXE)
Command Error (CME)
Not used.
Power On
All commands previous to receipt of an *OPC command
have been executed. Interface is ready to accept another
message.
Always set to 0.
Attempt has been made to read data from the meter’s
output buffer when no output is present or pending. Or, a
new command line has been received before a previous
query has been read. Or, Both input and output buffers are
full.
Incorrect input during calibration, or RS-232 input buffer
overflow.
Command was understood but could not be executed.
Result, for example, of an inappropriate parameter.
Command was not executed because it was not
understood. This condition could result, for example, if a
command sent to the meter contained a syntax error.
Always set to 0.
(PON) Power has been cycled off and on since the last
time the ESR was read or cleared.
Status Byte Register
The Status Byte Register (STB) is a binary-encoded register that contains eight bits. Note
that the Service Request Enable Register (SRE) uses bits I through 5 and bit 7 to set bit 6,
the request service (RQS) bit, as enabled by the SRE. When the RQS bit is set true(l), the
meter sets the SRQ line true (1), which generates a service request. The eight bits of the
Status Byte Register (as read by the *STB? command) are described in Table 5-7.
Reading the Status Byte Register
The host can read the Status Byte Register by taking a serial poll or sending the meter a
"*STB?" query. The value of the status byte is not affected by the STB? query. When the
Status Byte Register is read, an integer is returned. This integer is the decimal equivalent
of an 8-bit binary number. [For example 48 is the decimal equivalent of the binary
00110000, and means that bit 4 (MAY) and bit 5 (ESB) are set to "1".]
If the status byte is read by serial poll, bit 6 is returned as a request service (RQS); if it is
read with an "*STB?" query, bit 6 is returned as Master Summary Status (MSS).
EXAMPLE EXPLANATION
*STB? Reads the Status Byte Register. Assume that "32" is returned. Converting 32
to the binary 00100000 indicates that bit 5 (ESB) is set to 1. To determine the
event status, you would have to read the Event Status Register in the same
manner, using the "ESR?" command.