Interfaces and Connectors
Bengal (VL-EPMe-30) Reference Manual
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SPI is, in its simplest form, a three wire serial bus. One signal is a clock, driven only by the
permanent master device on-board. The others are Data In and Data Out with respect to the
master. The SPX implementation adds additional features, such as chip selects and an interrupt
input to the Master. The master device initiates all SPI transactions. A slave device responds
when its chip select is asserted and it receives clock pulses from the master.
The SPI clock rate can be software configured to operate at speeds between 1 MHz and 8 MHz.
Because this clock is divided from a 33 MHz PCI clock, the actual generated frequencies are not
discrete integer MHz frequencies. All four common SPI modes are supported through the use of
clock polarity and clock idle state controls.
VersaLogic SPX Expansion Modules
VersaLogic offers several SPX modules that provide a variety of standard functions, such as
analog input, digital I/O, CANbus controller, and others. These are small boards (1.2 x 3.78
inches) that can mount on the PC/104 stack, using standard standoffs, or up to two feet away
from the baseboard. For more information, contact VersaLogic at [email protected].
