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Model 845-M Programmer’s Manual V1.1 2011
Transition Filter
The transition filter is a special register that specifies which types of bit state changes in the condition
register will set corresponding bits in the event register. Negative transition filters (NTR) are used to
detect condition changes from True (1) to False (0); positive transition filters (PTR) are used to detect
condition changes from False (0) to True (1). Setting both positive and negative filters True allows an
event to be reported anytime the condition changes. Transition filters are read-write. Transition filters
are unaffected by queries or *CLS (clear status) and *RST commands. The command :STATus:PRESet sets all
negative transition filters to all 0’s and sets all positive transition filters to all 1’s.
Event Register
The event register latches transition events from the condition register as specified by the transition
filter. Bits in the event register are latched, and once set they remain set until cleared by a query or a
*CLS command Event registers are read only.
Enable Register
The enable register specifies the bits in the event register that can produce a summary bit. The Model
845-M logically ANDs corresponding bits in the event and enable registers, and ORs all the resulting
bits to obtain a summary bit. Summary bits are recorded in the Summary Status Byte. Enable registers
are read-write. Querying an enable register does not affect it. The command
:STATus:PRESet sets the Operation Status Enable register and the Questionable Status Enable register
to all 0’s.
Status Group Reporting
The state of certain Model 845-M hardware and operational events and conditions can be determined
by programming the status system. Three lower status groups provide status information to the
Summary Status Byte group. The Summary Status Byte group is used to determine the general nature of
an event or condition and the other status groups are used to determine the specific nature of the
event or condition.
Summary Status Byte Group
The Summary Status Byte group, consisting of the Summary Status Byte Enable register and the
Summary Status Byte, is used to determine the general nature of an Model 845-M event or condition.
The bits in the Summary Status Byte provide the following:
Operation Status Group
