Interfaces and Connectors
37
Lion (VL-EPMe-42) Reference Manual
Table 23. SPX Expansion Bus Pinout
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 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 0.75 MHz and 6
MHz. Because this clock is divided from a 24Mhz LPC 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.
.
Pin
Signal/
Function
Direction
Description
1
VCC
Out
5V Power (S0 power in this product)
2
SCLK
Out
SPX Clock
3
GND
--
4
MISO
In
Serial Data input
5
GND
--
6
MOSI
Out
Serial Data output
7
GND
--
8
SS0#
Out
Chip Select 0 (low true)
9
SS1#
Out
Chip Select 1 (low true)
