Chapter 3
Theory of Operation
© National Instruments Corporation
3-5
SCXI-1162 User Manual
This circuitry is divided into an SCXI digital interface section and rear connector interface
section.
The SCXI digital interface buffers signals from the SCXIbus to the module and drives signals
from the module onto the SCXIbus.
The rear connector routing circuit determines the function of the rear connector from the jumper
settings. The rear connector interface configures the rear connector for connection to either a
DIO-type or an MIO-type data acquisition board. It also determines from the setting of jumper
W2 whether to route the data signal directly to the rear connector in parallel or whether to
establish a serial communication link to the SCXIbus interface. If the routing is to be in parallel,
then the rear connector interface determines from jumper W1 whether to drive lines 0 through 31
or only lines 0 through 23.
Register Circuitry
Figure 3-4 diagrams the SCXI-1162 register circuitry.
Address 0001
Address 0000
Serial Data In
Module ID
Register
Data
Register
Serial Data Out
Address Handler
Serial Controls In
Figure 3-4. SCXI-1162 Register Circuitry
The register circuitry section consists of the Address Handler, the Data Register, and the Module
ID Register.
The Data Register contains a 4-byte parallel-in serial-out shift register. When the SS* line is low
(indicating that the module slot has been selected) and the address handler has selected address
0001, data from the isolated inputs is loaded into the Data Register when the D*/A line goes low
(indicating a data transfer). After each downward transition of SPICLK, one data bit is clocked
out, starting with bit 31. After all 32 bits are clocked out, D*/A must make another high-to-low
transition to reload the data.
The Module ID Register connects to MISO on the SCXIbus. The Module ID Register is a read-
only 4-byte parallel-in serial-out shift register and an SPI communication adapter. The address
of the Module ID Register is hex 0000. The contents of the Module ID Register are written onto
MISO during the first four bytes of transfer after you select the Module ID Register in the
Address Handler. The Module ID Register will write zeros to MISO thereafter until you deselect
the Module ID Register. The SCXI-1162 module ID is hex 00000010.
