National Instruments SCXI-1163 - Manual (Page 45)

Theory of Operation Chapter 3
SCXI-1163 User Manual 3-6 © National Instruments Corporation
The register circuitry section consists of the Data Register, the Module ID Register, the Output
Mode Register, and the Primary Mode Status Register.
The Data Register is a 4-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, D*/A indicates data
transfer (D*/A low), and the Data Register address was selected in the Address Handler. When
the output mode of operation is set to serial, the Data Register controls the state of the
SCXI-1163 outputs. Two addresses can access the Data Register–0001 and 0006 (hexadecimal).
Selecting 0001 will set the output mode to serial, and selecting 0006 will return the output mode
to the primary mode. The complete descriptions of the register bits are given in Chapter 4,
Register Descriptions . Writes to the Data Register require the following steps:
1. SS* goes low, enabling communication with the board.
2. Write 0001 or 0006 (hexadecimal) to the Address Handler. This selects the Data Register.
3. D*/A goes low, indicating that the information sent on the MOSI line is data.
4. The serial data is available on MOSI and SPICLK clocks it into the register.
5. SS* goes high and D*/A goes high, indicating an end of communication. This action latches
the Data Register bits.
At reset or at power up, the states of the outputs of the Data Register are set to logic states.
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 selecting the Module ID Register in the Address
Handler. Zeros are written to MISO thereafter until the Module ID Register is deselected. The
SCXI-1163 module ID is hex 00000012.
The Output Mode Register is a 1-bit register that determines the output mode of operation. Set it
to serial mode by writing to the Data Register at address 0001; write to address 0006 to return to
the primary mode of operation. You can read the output mode by selecting address 0003, pulling
D*/A low, and reading the value on the MISO line. A logic low indicates that the output mode is
set to parallel, whereas a logic high indicates that the output mode is set to serial.
The Primary Mode Status Register is a read-only register which returns the jumper-configured
primary mode of operation. To read the primary mode, select address 0002, pull D*/A low, and
read the value on the MISO line. A logic low indicates that the primary mode is set to serial,
whereas a logic high indicates that the primary mode is set to parallel.
Optically Isolated Output Channels
The SCXI-1163 consists of eight ports of four optically isolated digital outputs. Each port of
outputs has an isolated connection for the Vcc and ground. The outputs of each port are
referenced to their particular grounds and powered by their particular Vccs; therefore, for any
port of outputs to work, a Vcc and a ground must be connected to that particular port. The Vcc,
ground, and four outputs of one port are isolated from the Vcc, ground, and four outputs of any
other port, and are isolated from the internal circuitry of the module. Vcc should be 5 V
±
.5 V above the ground for a given port. Figure 3-5 represents one of the optically isolated