Keithley 486 Instruction Manual page 107

SECTION 4
IEEE-488 Reference
Serial Poll Byte Format -The serial poll byte contains information relating to data and error
conditions within the instrument. The general format of the status byte (which is obtained by
using the serial polling sequence, as described in paragraph 4.3.7) is shown in Figure 4-5. Note
that the various bits correspond to the bits in the SRQ mask as described above.
The bits in the serial poll byte have the following meanings:
Bit 0 (Reading Overflow) - Set when an overrangedreading has been made. Cleared when an
on-scale reading has been made.
Bit 1 (Data Store Full) - Set when the defined data store size is full. Cleared by re-arming the
data store.
Bit 2 (Data Store l/2 Full) - Set when half the defined data store size is full. Cleared by rearm-
ing the data store.
Bit 3 (Reading Done) -Set when the instrument has completed the present reading conver-
sion. Cleared after the instrument has sent a reading.
Bit 4 (Ready) -Set when the instrument has processed all previously received commands and
is ready to accept additional commands or triggers. Cleared while the
instrument
is processing
commands or triggers.
Bit 5 (Error) - Set when one of the following errors have occurred:
1. IDIX
2. IDDCO
3. NoRemote
4. selftest
5. Trigger Ovemm
6. conflict
7. CalLocked
8. Zero Check
9. Calibration Error
10. ETROM Defaults Error
11. ETROM Cal Constants Error
12 V-Source Conflict (Model 487)
13. Interlock &lode1 487)
This bit is cleared when theU1 status wordisread to determine the type of error (see paragraph
4.2.19).
Bit 6 (RQS = Request for Service) - Set if the Model 486/487 asserted SRQ. Cleared when the
instrument is serial polled.
Bit 7 (Voltage Source Error) - Set if the voltage source of the Model 487 becomes current lim-
ited or the interlock becomes unsafe. Cleared when the U9 status word is read after the voltage
source errors are corrected. For the Model 486, this bit is always cleared (0).