5790B
Operators Manual
6-78
Instrument Status Change Registers
There are two registers dedicated to monitoring changes in the ISR. These are
the ISCR0 (Instrument Status 1-0 Change Register) and the ISCR1 (Instrument
Status 0-1 Change Register). Each status change register has an associated
mask register. Each ISCR is cleared (set to 0) when the Product is turned on,
every time it is read, and at each *CLS (Clear Status) command.
Instrument Status Change Enable Registers
The Instrument Status Change Enable registers (ISCE0 and ISCE1) are mask
registers for the ISCR0 and ISCR1 registers. If a bit in the ISCE is enabled (set to
1) and the corresponding bit in the ISCR makes the appropriate transition, the
ISCB bit in the Status Byte is set to 1. If all bits in the ISCE are disabled (set to
0), the ISCB bit in the Status Byte never goes to 1. The contents of the ISCE
registers are set to 0 at power-up.
Bit Assignments for the ISR, ISCR, and ISCE
See Table 6-11 for the ISR, ISCR, and ISCE bit assignments.
Table 6-11. Bit Assignments for the ISR, ISCEs and ISCRs
15 14 13 12 11 10 9 8
0 REMOTE
ZERO
CAL
0 0 0 0 0
7 6 5 4 3 2 1 0
0 0 MCCHG MDCHG INPCHG RNGCHG VALID BUSY
REMOTE Set to 1 when the product is under remote control.
ZERO CAL When 1, DC Zero Cal is necessary.
MCCHG
Set to 1 when measurement controls have changed. (Measurement controls are
EXTGUARD, EXTRIG, DFILT, AUTORANGE, HIRES.)
MDCHG
Set to 1 when an operating mode has changed. (Modes are MEASUREMENT,
CALIBRATION, DIAGNOSTIC, and CALWAITING.) This bit is always 0 in the ISR.
It changes to 1 only in the ISCR0 and ISCR1 registers.
INPCHG
Set to 1 when the input source has changed. This bit is always 0 in the ISR. It
changes to 1 only in the ISCR0 and ISCR1 registers.
RNGCHG
Set to 1 when the range has changed. This bit is always 0 in the ISR. It changes to
1 only in the ISCR0 and ISCR1 registers.
VALID Set to 1 when the present measurement is valid.
BUSY
Set to 1 when the Product is making a measurement, running a calibration or
diagnostics procedure, or saving anything to nonvolatile memory.
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