Content originally posted in LPCWare by Carrigan on Tue Mar 06 07:24:07 MST 2012
Page 14 of the LPC1114 User manual has a great picture of the clock setup of this device. You can see here that the "System Clock" coming out of the SYSAHBCLKDIV block is tied to both the Cortex-M0 processor as well as the AHBCLKCTRL control register. Since there is not an individual clock for the I2C like there is for SPI and UART, this means that the clock coming in to the I2C module is the same as the system clock.
Note that you will have to divide this clock using the SCLH and SCLL registers to bring it down to acceptable values (pg 166). The maximum frequency that the 1114 supports is 1MHz in Fast-mode Plus.
