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Digital Control Circuitry
Serial Data Out
Input Channel
Select
© National Instruments Corporation
Figure 3-4 diagrams the SCXI-1121 digital control.
Module ID Register
Configuration
Output
Stage
Control
Figure 3-4. SCXI-1121 Digital Control
The digital control section consists of the Configuration Register and the
Module ID Register.
The Configuration Register is a two-byte, serial-in parallel-out shift
register. Data is received on the MOSI line from either Slot 0 or the data
acquisition board when SS* is enabled and D*/A indicates data transfer
(D*/A low). The Configuration Register provides temperature channel
selection and channel selection, and configures the SCXI-1121 for
scanning options. All the control bits are fed into a latch before being
routed to the rest of the module. The channel-select bits are taken directly
from the shift register. Complete descriptions of the register bits are given
in Chapter 4,
Register
require the following steps:
1.
SS* goes low, enabling communication with the board.
2.
D*/A goes low, indicating that the information sent on the MOSI line
is data.
Register
SCANCLK
Path
Control
Hardware
Scan
Control
Descriptions. Writes to the Configuration Register
3-7
Chapter 3
Theory of Operation
Buffered
Serial Data In
Buffered Digital
Control Signals
SCXI-1121 User Manual
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