Chapter 4 Theory of Operation
SCXI-1161 User Manual 4-4
©
National Instruments Corporation
signals from the data acquisition board and the SCXIbus and sends
signals back and forth between the data acquisition board and the
SCXIbus.
Digital Control Circuitry
Figure 4-3 diagrams the SCXI-1161 digital control.
Figure 4-3. SCXI-1161 Digital Control
The digital control section consists of the Data Register and the Module
ID Register.
The Data Register is a 2-byte serial-in, parallel-out shift register with
relay drive capabilities. The Data Register controls the state of the
SCXI-1161 relays. The complete descriptions of the register bits are
given in the SCXI Register-Level Programmers Manual.
At reset or at power up, the relays are set to the NC position.
The Module ID Register is an 8-bit parallel serial-in, serial-out shift
register. The contents of the Module ID Register are written onto MISO
during the first four bytes of transfer after you select the module. Zeros
are written to MISO thereafter until you deselect the module. The
SCXI-1161 module ID is hex E.
Buffered
Serial Data In
Buffered Digital
Control Signals
Data Register
Module ID Register
NO NO
<7..4> <3..0>
Serial Data Out