Measurement Computing Analyzer488 - Manual (Page 30)

Section 2 Getting Started
2.8
2.4 Detailed Operation
This section describes the operation of the Analyzer488 hardware. It includes
terminology, a description of the IEEE 488 bus handshaking control, bus recording
with and without triggering, time and rate measurement, and analyzing results.
2.4.1 Analyzer488 Terminology
Asserted The "asserted" state of a signal is the logical true state of
that signal regardless of whether high true or low true logic
is being used.
Unasserted The "unasserted" state of a signal is the logical false state of
that signal regardless of whether high true or low true logic
is being used.
Bus State The logical state of the IEEE 488 bus data lines,
management lines and handshake lines.
Bus Lines Refers to the five bus management lines, three handshake
lines, and eight bus data lines. The management lines are
Attention (ATN), Interface Clear (IFC), Remote Enable
(REN), End or Identify (EOI), and Service Request (SRQ).
Bus Handshake Used to refer to the three-wire IEEE 488 bus handshake
lines. The handshake lines are Data Available (DAV), Not
Ready for Data (NRFD), and Not Data Accepted (NDAC).
Bus Event A bus event is a transaction on the bus. The term "bus
event" indicates an action on the bus that will force the
Analyzer488 to record the bus state. These events include
asserting DAV, asserting IFC, and asserting EOI after
asserting ATN (Parallel Poll). Bus events are sensed in an
edge-sensitive manner. If a bus event occurs, subsequent
bus events cannot be recorded until the first bus event
terminates, i.e. if IFC is asserted, assertion of the DAV
signal will not be recognized until IFC is unasserted.