The clock speed of a CoIDE project is set on a default of 100Mhz. Timer interrupts are dependent on the clock speed, therefore it can be useful to change the clock speed. At lower clock speeds the Simplecortex also consumes less energy, for energy efficient designs it can be useful to lower the clock speed.To change the clock speed open the "cmsis_boot" folder in the project and open "system_LPC17xx.c". In "system_LPC17xx.c search " for the following line:
#define PLL0CFG_Val 0x00050063
The value 0x00050063 can be changed. With a value of 0x00050063 the Simplecortex runs at 100Mhz. To run at 120Mhz, change this value to 0x00050077. Other frequencies are also possible. To run it at 72Mhz for example convert 72 to hexadecimal numbger and subtract 1. For 72Mhz you get the hexadecimal value 47. Now replace de last 2 digits of 0x00050063 with these digits. So to run the Simplecortex at 72Mhz change 0x00050063 to 0x00050047. The Simplecortex can run at 120Mhz max, higher frequencies are not supported. Lower frequencies then 60Mhz are also not recommended. Changing the clockspeed above or below these frequencies might result in bricked Simplecortex boards! If this happens, it is always possible to do a master reset on the chip.