Keysight E4981A Programming Manual page 365

Status Reporting System
General Status Register Model
The transition filter enables you to select a positive and/or negative transition
of the condition register bit in order to set a bit in the corresponding event
register. For example, using the negative transition filter to set bit 3 to "1"
causes bit 3 of the event register to be set to "1" when bit 3 of the condition
register makes a negative transition, that is, changes from 1 to 0.
Figure C-2 Transition filter and condition register
The E4981A's condition register and transition filter work only with the
operation status register. However, the E4981A's transition filter's setting is
fixed so that bits 5, 8, 9, 10 of the event register are set to "1" when the
condition register makes a positive transition (i.e., changes from 0 to 1) and
bits 1, 2, 3, 4, 7, 12 of the event register are set to "1" when the condition
register makes a negative transition (i.e., changes from 1 to 0).
Keysight E4981A 120 Hz/1 kHz/1 MHz Capacitance Meter 365