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Theory of Operation
Chapter 3
SCXI-1100 User Manual
3-6
© National Instruments Corporation
Pin
Signal Name
Description (continued)
B23
SPICLK
Serial Peripheral Interface (SPI) Clock – Clocks the
serial data on the MOSI and MISO lines. Open
collector. I/O.
C23
MOSI
Master-Out-Slave-In – Transmits data from the
SCXIbus to the module. Open collector. I/O.
A24
TRIG0
TRIG0 – General-purpose trigger line that the
SCXI-1100 uses to send SCANCLK to other
modules or receive SCANCLK from other modules.
Open collector. I/O.
B24
SS*
Slot Select – When low, enables module
communications over the SCXIbus. Totem pole.
Input.
C24
SCANCON
Scanning Control – Combination output enable and
reload signal for scanning operations. Totem pole.
Input.
* Indicates active low
All other pins are not connected.
MOSI, MISO, SPICLK, and SS* form a synchronous communication link that conforms with
SPI using an idle-high clock and second-edge data latching. D*/A, INTR*, and RESET* are
additional control signals.
When the module is installed in an SCXI-1000 or SCXI-1001 chassis, the data acquisition board,
via the module rear signal connector, must tap into the open-collector backplane signal lines as a
master to write to the module. Table 3-1 shows the signal connections from the rear signal
connector to the backplane.
Table 3-1. SCXIbus Equivalents for the Rear Signal Connector
Rear Signal Connector
Signal
SCXIbus Equivalent
SERDATIN
MOSI
DAQD*/A
D*/A
SLOT0SEL*
INTR*
You must set jumper W11 to position A
(Revision A and B modules only)
SERCLK
SPICLK
SERDATOUT
MISO
You must set jumper W5 to position 3
The SCXI-1100 module converts the data acquisition board signals to open-collector signals on
the backplane of the SCXI chassis. For the data acquisition board to talk to a slot, the board must
first assert the SS* for that slot. This is done by asserting INTR* low, writing a 16-bit number
over MOSI corresponding to the desired slot (and chassis if you are using an SCXI-1001