Interfaces and Connectors
EBX-22 Reference Manual
62
SPI
L
EGACY
M
ODE
The following tables describe the legacy SPI control registers (SPICONTROL and SPISTATUS)
and data registers (SPIDATA3-0), such as those used on the EBX-11. To enable SPI legacy
mode, the SPI field (bits D6-D5) of the MODCON register (1DFh) must be set to 1h.
SPICONTROL (READ/WRITE) 1D8h
D7 D6 D5 D4 D3 D2 D1 D0
CPOL
CPHA SPILEN1 SPILEN0 MAN_SS
SS2
SS1
SS0
Table 31: SPI Control Register 1 Bit Assignments
Bit Mnemonic
Description
D7 CPOL
SPI Clock Polarity –
Sets the SCLK idle state.
0 = SCLK idles low
1 = SCLK idles high
D6 CPHA
SPI Clock Phase –
Sets the SCLK edge on which valid data will be read.
0 = Data read on rising edge
1 = Data read on falling edge
D5-D4 SPILEN
SPI Frame Length –
Sets the SPI frame length. This selection works in
manual and auto slave select modes.
SPILEN1 SPILEN0 Frame Length
0
0
8-bit
0
1
16-bit
1
0
24-bit
1
1
32-bit
D3 MAN_SS
SPI Manual Slave Select Mode –
This bit determines whether the slave select
lines are controlled through the user software or are automatically controlled by
a write operation to SPIDATA3 (1DDh). If MAN_SS = 0, then the slave select
operates automatically; if MAN_SS = 1, then the slave select line is controlled
manually through SPICONTROL bits SS2, SS1, and SS0.
0 = Automatic, default
1 = Manual
D2-D0 SS
SPI Slave Select –
These bits select which slave select will be asserted. The
SSx# pin on the base board will be directly controlled by these bits when
MAN_SS = 1.
SS2 SS1 SS0 Slave Select
0 0 0 None,
port
disabled
0
0
1
SPX Slave Select 0, J17 pin-8
0
1
0
SPX Slave Select 1, J17 pin-9
0
1
1
SPX Slave Select 2, J17 pin-10
1
0
0
SPX Slave Select 3, J17 pin-11
1
0
1
On-Board A/D Converter Slave Select
1
1
0
On-Board Digital I/O Ch 0-Ch 15 Slave Select
1
1
1
On-Board Digital I/O Ch 16-Ch 31 Slave Select
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