Measurement Computing Analyzer488 - Manual (Page 32)

Section 2 Getting Started
2.10
Analyzer488 unasserts the bus NDAC line for each Step, or from 1 to 10
times a second if Slow handshaking is used.
If the Analyzer488 is to talk or listen on the bus it must be in one of
the handshake modes, Fast, Slow, or Step. To view the data transactions on
the bus as they occur, either Slow or Step handshaking speeds may be used.
If the Analyzer488 is used to control the flow of data on the bus, then Step
handshaking must be used to hold off and step through bus transactions.
If the Analyzer488 is used to monitor an active bus at full speed,
either Fast handshaking or no handshaking (None) may be used. If the
Analyzer488 is used to detect bus errors, it must be used with None
handshake otherwise the Analyzer488 will complete a handshake on the bus
when a bus error would normally occur.
2.4.3 Bus Recording System
The bus recording system is used to record bus events for later
analysis. When recording is enabled, the Analyzer488 stores the state of the
bus data lines and bus management lines, the bus error state, the state of the
trigger signal, and a Not Empty flag into record memory when bus events
occur on the IEEE 488 bus. The Analyzer488 can record 32,768 bus events
at a maximum rate of 1 MegaByte/second.
The record memory in the Analyzer488 is organized as a circular
buffer. If more than 32,768 bus events occur while recording, only the
latest 32,768 bus events will be stored, the earlier recorded events are
overwritten.
The recording system is enabled and disabled by a simple command or
keypress and may operate with any of the handshake selections. Bus events
cause the Analyzer488 to record regardless of their source. If the
Analyzer488 is talking while recording is enabled, these bus events will be
recorded.
The recording system includes a trigger mechanism which may be
used to automatically disable recording or switch the handshake selection to
Step upon satisfying specified conditions. The trigger system is described
in more detail in section 2.4.6.