Digital Interface; Figure 3-3. Digital Interface Circuitry Block Diagram - National Instruments SCXI-1121 User Manual

Chapter 3 Theory of Operation

Digital Interface

Buffered Serial
Data
Buffered Digital
Signal Controls
SCXI-1121 User Manual
chassis is being used), and then releasing INTR* high. At this point, SS* of
the desired slot is asserted low and the data acquisition board can
communicate with the module in that slot according to the SPI protocol.
Figure 3-3 shows a diagram of the SCXI-1121 and SCXIbus digital
interface circuitry.
SCXIbus
Digital
Interface

Figure 3-3. Digital Interface Circuitry Block Diagram

The digital interface circuitry is divided into a data acquisition section
and an SCXIbus section. The SCXI-1121 connects to the SCXIbus via a
4 24 metral receptacle and to the data acquisition board via a 50-pin
ribbon-cable header. The digital interface circuitry buffers the digital
signals from the data acquisition board and from the SCXIbus and sends
signals back and forth between the data acquisition board and the SCXIbus.
SERDATIN
DAQD*/A
SLOT0SEL*
SERCLK
SERDATOUT
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