Measurement Process; Measurement Setup And Control - VXI VT1433B User Manual

VT1433B User's Guide
The Host Interface Library

Measurement Process

Measurement Setup and Control

When the VT1433B makes a measurement, the measurement itself consists of two
phases: the measurement initialization and the measurement loop. Each of these
phases consists of several states, through which the measurement progresses.
The transition from one state to the next is tied to a transition in the Sync/Trigger
line (one of the TTL trigger lines on the VXI back plane). A state (such as Idle)
begins when the Sync/Trigger line goes low. The Sync/Trigger line then remains
low as long as the state is in effect. When the Sync/Trigger line goes high it
signals the transition to the next state. See the sections "Measurement
Initialization" and "Measurement Loop" below for more details about these
transitions. During all the transitions of the Sync/Trigger line, the clock line
continues with a constant pulse.
The Sync/Trigger line is "wire-OR'd" such that all modules in a multiple-module
system (within one mainframe) must release it for it to go high. Only one
VT1433B is required to pull the Sync/Trigger line low. In a system with only
one VT1432A, the Sync/Trigger line is local to the module and not is routed to a
TTL TRIGGER line on the VXI back plane.
Sync/Trigger Line Idle Trigger
Pre-arm Arm Meas
Start of End of
State State
Figure 4-3: Transitions between states
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