LSPCLK ,
(SPIBRR 1)+
LSPCLK ,
4
SM320F2812-HT
SGUS062A–JUNE 2009 –REVISED APRIL 2010
www.ti.com
4.7 Serial Peripheral Interface (SPI) Module
The F2812 device includes the four-pin serial peripheral interface (SPI) module. The SPI is a high-speed,
synchronous serial I/O port that allows a serial bit stream of programmed length (one to sixteen bits) to be
shifted into and out of the device at a programmable bit-transfer rate. Normally, the SPI is used for
communications between the DSP controller and external peripherals or another processor. Typical
applications include external I/O or peripheral expansion through devices such as shift registers, display
drivers, and ADCs. Multidevice communications are supported by the master/slave operation of the SPI.
The SPI module features include:
• Four external pins:
– SPISOMI: SPI slave-output/master-input pin
– SPISIMO: SPI slave-input/master-output pin
– SPISTE: SPI slave transmit-enable pin
– SPICLK: SPI serial-clock pin
NOTE
All four pins can be used as GPIO, if the SPI module is not used.
• Two operational modes: master and slave
• Baud rate: 125 different programmable rates
– Baud rate when BRR ≠0
=
= when BRR = 0, 1, 2, 3
Serial port performance is limited by I/O buffer switching speed. Internal prescalers must be adjusted
such that the peripheral speed is less than the I/O buffer speed limit—20 MHz maximum.
• Data word length: one to sixteen data bits
• Four clocking schemes (controlled by clock polarity and clock phase bits) include:
– Falling edge without phase delay: SPICLK active-high. SPI transmits data on the falling edge of the
SPICLK signal and receives data on the rising edge of the SPICLK signal.
– Falling edge with phase delay: SPICLK active-high. SPI transmits data one half-cycle ahead of the
falling edge of the SPICLK signal and receives data on the falling edge of the SPICLK signal.
– Rising edge without phase delay: SPICLK inactive-low. SPI transmits data on the rising edge of the
SPICLK signal and receives data on the falling edge of the SPICLK signal.
– Rising edge with phase delay: SPICLK inactive-low. SPI transmits data one half-cycle ahead of the
falling edge of the SPICLK signal and receives data on the rising edge of the SPICLK signal.
• Simultaneous receive and transmit operation (transmit function can be disabled in software)
• Transmitter and receiver operations are accomplished through either interrupt-driven or polled
algorithms.
• Nine SPI module control registers: Located in control register frame beginning at address 7040h.
NOTE
All registers in this module are 16-bit registers that are connected to Peripheral Frame 2.
When a register is accessed, the register data is in the lower byte (7–0), and the upper byte
(15–8) is read as zeros. Writing to the upper byte has no effect.
76 Peripherals Copyright © 2009–2010, Texas Instruments Incorporated
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