spi_mode0.c

spi协议的驱动程序源代码

//-----------------------------------------------------------------------------
// SPI_MODE0.c
//-----------------------------------------------------------------------------
// Copyright 2001 Cygnal Integrated Products, Inc.
//
// AUTH: BD
// DATE: 14 DEC 01
//
// This file contains a ‘C’ Implementation of a Mode 0 Master SPI device.
//
// Target: C8051F30x
// Tool chain: KEIL C51 6.03 / KEIL EVAL C51
//
//
#include <c8051f300.h> // SFR declarations
#include “SPI_defs.h” // SPI port definitions
//-----------------------------------------------------------------------------
// SPI_Transfer
//-----------------------------------------------------------------------------
//
// Simultaneously transmits and receives one byte <SPI_byte> using
// the SPI protocol. SCK is idle-low, and bits are latched on SCK rising.
//
// Timing for this routine is as follows:
//
// Parameter Clock Cycles
// MOSI valid to SCK rising edge 6
// SCK rising to MISO latched 2
// SCK falling to MOSI valid 7
// SCK high time 8
// SCK low time 13
char SPI_Transfer (char SPI_byte)
{
unsigned char SPI_count; // counter for SPI transaction
for (SPI_count = 8; SPI_count > 0; SPI_count--) // single byte SPI loop
{
MOSI = SPI_byte & 0x80; // put current outgoing bit on MOSI
SPI_byte = SPI_byte << 1; // shift next bit into MSB
SCK = 0x01; // set SCK high
SPI_byte |= MISO; // capture current bit on MISO
SCK = 0x00; // set SCK low
}
return (SPI_byte);
} // END SPI_Transfer