Measurement Computing Analyzer488 - Manual (Page 31)

Section 2 Getting Started
2.9
Bus Error A bus error occurs when a talker on the IEEE 488 bus
attempts to transfer data by asserting the DAV signal and
finds that the NRFD and NDAC handshake signals are both
unasserted, indicating no listeners are present. The
Analyzer488 is capable of recording bus errors.
Bus Record The bus events that the Analyzer488 records are stored as
bus records. These records include the state of the bus data
lines and bus management lines. The Analyzer488 does not
record the state of the bus handshake lines directly, but
records a single bit which signifies whether or not a bus
error occurred on the event. Additionally, a bit indicating
the position of a trigger point and a Not Empty indicator bit
are recorded.
2.4.2 Handshaking and Controlling the Speed of the Bus
When connected to an IEEE 488 bus, the Analyzer488 is capable of
participating in, or not participating in, the bus three-wire handshake. The
Analyzer488 handshaking is used with all Analyzer488 bus operations
including viewing, recording, and controlling events on the IEEE 488 bus.
When participating, the Analyzer488 acts as either a source (Talker) or
acceptor (Listener). When not participating in handshaking (NONE
handshake selection), the Analyzer488 monitors the bus without affecting
bus transfer rates or appearing to be a listener.
Three general data transfer rates may be used for both source and
acceptor handshaking. The three rates are defined as Fast (up to 1
MegaByte/Second), Slow (1 to 10 Bytes/Second) and Step (single-step
operation).
The Fast handshake selection allows the Analyzer488 to perform data
transfers on the IEEE 488 bus at the maximum transfer rate of the bus, 1
MegaByte/Second. Slow handshaking and Step handshaking allow the
Analyzer488 to control the speed of bus transfers on the IEEE 488 bus at
rates below 10 Bytes/Second.
When configured as a Talker, the Analyzer488 will assert the DAV
line when set to Step handshaking. It will assert DAV from 1 to 10 times a
second if Slow handshaking is used. When configured as a Listener, the