Industrial I/O Functions And Spi Interface - VersaLogic Python EBX-11 Reference Manual

Industrial I/O Functions and SPI Interface

The EBX-11 employs a set of I/O registers for controlling on-board analog input, digital I/O, and
external serial peripheral interface (SPI) devices. These functions share control and data registers
located at I/O addresses 1D8h through 1DDh.
The SPI bus specifies four logic signals:
 SCLK – Serial clock (output from master)
 MOSI – Master output, slave input (output from master)

MISO – Master input, slave output (output from slave)
 SS – Slave select (output from master)
The EBX-11 SPI implementation adds additional features, such as hardware interrupt input to the
master. The master initiates all SPI transactions. A slave device responds when its slave select is
asserted and it receives clock pulses from the master.
Slave selects are controlled in one of two modes: manual or automatic. In automatic mode, the
slave select is asserted by the SPI controller when the most significant data byte is written. This
initiates a transaction to the specified slave device. In manual mode, the slave select is controlled
by the user and any number of data frames can be sent. The user must command the slave select
high to complete the transaction.
The SPI clock rate can be software configured to operate at speeds between 1 MHz and 8 MHz.
All four common SPI modes are supported through the use of clock polarity and clock phase
controls.
To initiate an SPI transaction, configure SPI registers SPICONTROL and SPISTATUS as shown
in Table 23 and Table 24 for the desired I/O device. For additional information on
communicating with specific SPI devices, please refer to their respective manufacturer's
datasheets. Table 22 lists configuration values for on-board SPI devices.
Analog Input
I/O Port Value
1D8h 15h
1D9h 30h
1DAh 00h
1DBh 00h
1DCh 00h
1DDh XXh
EBX-11 Reference manual
Table 22: Analog Input and Digital I/O Register Values
Description
Idle low, rising edge, 16-bit
frame length, automatic slave
select, ADC_SS
8 MHz, IRQ disabled, MSbit
shift
Not used in 16-bit frame
Not used in 16-bit frame
Any value, data ignored
XX = A/D channel (0-7),
written to bits 5-3
Interfaces and Connectors
Digital I/O
I/O Port Value
1D8h 26h Idle low, rising edge, 24-bit
frame length, auto slave select,
1D9h F8h IRQ10, 8 MHz, hardware IRQ
enabled, MSbit shift
1DAh 00h Not used in 24-bit frame
1DBh XXh
1DCh XXh
1DDh XXh
Description
DIO_0_SS
Data byte
Address byte
Command byte
44