/*******************************************************************************
* API FUNCTION DEFINITIONS
*******************************************************************************/
/**
* \brief This API will divide the system clock fed to I2C module between
* 12 and 100Mhz.It will also configure the I2C bus clock frequency.
*
* \param baseAdd It is the Memory address of the I2C instance used.
* \param sysClk It is the System clock fed to I2C module.
* \param internalClk It is the internal clock used by I2C module.Which is
* obtained by scaling System clock fed to I2C module.
* \param outputClk It is the required I2C bus speed or frequency.
*
* \return None.
**/
void I2CMasterInitExpClk(unsigned int baseAdd, unsigned int sysClk,
unsigned int internalClk, unsigned int outputClk)
{
unsigned int prescalar;
unsigned int divider;
/* Calculate prescalar value */
prescalar = (sysClk / internalClk) - 1;
HWREG(baseAdd + I2C_PSC) = prescalar;
divider = internalClk/outputClk;
divider = divider / 2;
HWREG(baseAdd + I2C_SCLL) = divider - 7;
HWREG(baseAdd + I2C_SCLH) = divider - 5;
}
倒数第三行除以二怎么来的呢？？
Fast/Standard mode SCL low time.
I2C master mode only, (FS).
This
8-bit value is used to generate the SCL low time value (tLOW) when
the peripheral is operated in master mode.
tLOW = (SCLL + 7) * ICLK time period, Value after reset is low (all 8
bits).
手册没写要除以二啊