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ADuC7023: Depending on how I configure POWCON1, I can disable the SPI and I2C - why is this happening?

Question asked by MikeL Employee on Sep 26, 2011
Latest reply on Sep 26, 2011 by MikeL

On the ADuC7023, I want to set the I2C baud rate to 20kHz:

POWKEY1  = 0x01;

POWCON0  = 0x00;           // 41.78Mhz as core clock

POWKEY2  = 0xF4;


POWKEY3  = 0x76;

POWCON1  = 0x002C;  // 10.44Mhz for I2C1

POWKEY4  = 0xB1;


I2C1DIV  = 0xFFFF;   // DIVH=255, DIVL=255


From this setting, the clock speed of I2C1 is calculated as below.


Fserial clock = 10.44Mhz / (2+255)+(2+255) = 20.3kHz.


But in this setting, I2C1 didn’t work correctly.(no response of SDA and SDK.)

Why does this happen??