Difference between revisions of "Unit SPI"

Revision as of 04:50, 2 September 2016

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Description

SPI (Serial Peripheral Interface) is a synchronous serial bus for communication with peripheral components.

The SPI protocol is not defined by any actual standard but some psuedo standards exist with all of the available devices. SPI is a master-slave protocol where the master asserts the chip selectline (CS) to select the slave device before sending data one byte at a time. For every byte written to the bus by the master the selected slave returns a byte as well so for every write there is an equivalent read. SPI can also operate in either 4 wire (standard) or 3 wire(bidirectional) modes.

Due to the lack of formal standards and the range of devices that exist various options are provided to allow setting clock phase and polarity as well chip select polarity.

For the purpose of this interface a device is the SPI controller attached to the local system and may be either a master or a slave. Since the protocol does not include any form of enumeration or identification the interface does not attempt to represent the devices connected to the bus, any driver written to communicate with a connected SPI device should know (or allow configuration of) the chip select for the for the device and the specific message format required for that device.

Constants

To be documented

Type definitions

To be documented

Public variables

To be documented

Function declarations

Initialization functions

procedure SPIInit;

SPI functions

function SPIDeviceStart(SPI:PSPIDevice; Mode,ClockRate,ClockPhase,ClockPolarity:LongWord):LongWord;

function SPIDeviceStop(SPI:PSPIDevice):LongWord;

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