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Front Panel SRQ
When
this bit is set to a 1 it indicates
that the front panel
Bit 4
SRO
button
has been
pressed.
This bit is cleared
when
the
3468A is Serial Polled.
Calibration Fail
This bit is used to indicate that an attempted calibration has
Bit 5
failed. The bit will be set to 1 under this condition. A Serial
Poll will clear this bit.
bits 1-5 and 7 are cleared.
Power-on
Reset
This bit is set to 1 when
a power-on
reset has occurred.
If
Bit 7
switch 3 on the rear panel block of switches is set to the "1"
or up position, bit 6 will be true and the SRO message is sent.
Bit 7 is cleared when the 3468A is Serial Polled.
The Status Byte together with the Service Request (SRQ) Mask determine when
the Require Service (ROS) bit is to be set. Setting ROS causes SRO to be sent on
the HP-IL. A Serial Poll of the 3468A will clear SRO and it will remain clear until
another reason for setting ROS occurs. ROS on the other hand, is set if one or
more corresponding
bits in the Status Byte and SRO Mask are both set. RQS is
cleared whenever all corresponding bits are not both set. A Serial Poll then, may
cause ROS to be cleared but not in all cases. Bits 2, 4, 5, and 7 are cleared with
a Serial Poll.
Try this simple exercise.
1. Reset the 3468A.
This should be done by cycling the LINE switch. Without
setting the SRQ
mask,
perform a serial poll on the 3468A.
Remember
to check
the command
structure for the controller you are using. The status byte returned
by the 3468A
should
indicate that bits O and 7 are true. Many controllers will
show a value of "129".
Looking at Figure 4-4 we can see that the value 129 is
equal to the sum of the decimal values of bits O and 7. Bit 7 is true because of
the power-on/reset
that occurred.
Bit O indicates that a measurement
has been
made and data is ready. This step of the exercise simply serves to show that bits
in the status register may be true without causing the Service Request message to
be sent. Remember that when Service Request is sent, the SRO annunciator turns
on.
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