There mayor may not b e a command to read a particular condition
register.
Transition Filter
The
transition lter
species whichtypes of bit state changes in the
condition register will set corresp onding bits in the event register.
Transition lter bits may b e set for positiv e transitions (
PTR
),
negative transitions (
NTR
), or both. Positive means a condition
bit changes from 0 to 1. Negative means a condition bit changes
from 1 to 0. Transition lters are read-write. Transition lters
are unaected by
*CLS
(clear status) or queries. They are set to
instrument dependentvalues at p ower on and after
*RST
.
Event Register
The
event register
latches transition events from the condition
register, as sp ecied by the transition lter. Bits in the event register
are latched, and once set they remain set until cleared by a query or
a
*CLS
(clear status). There is no buering, so while an ev
ent bit is
set, subsequentevents corresp onding to that bit are ignored. Ev
ent
registers are read-only.
Enable Register
The
enable register
species the bits in the event register that
can generate a summary bit. The instrument logically ANDs
corresp onding bits in the event and enable registers, and ORs all
the resulting bits to obtain a summary bit. Summary bits are in
turn recorded in the Status Byte. Enable registers are read-write.
Querying an enable register do es not aect it. There is alwa
ys a
command to read and write to the enable register of a particular
status group.
An Example Sequence
Figure 1-34 illustrates the resp onse of a single bit position in a
typical status group for various settings. The changing state of the
condition in question is shown at the bottom of the gure. A small
binary table shows the state of the chosen bit in each status register
at the selected times T1 to T5.
Getting Started Programming 1-107
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