1.前言
Features of the SIM include:
System clocking configuration
（1）System clock divide values
（2） Architectural clock gating control
（3） USB clock selection and divide values
（4） SDHC clock source selection
（5） Ethernet 1588 timestamp and RMII clock source selection
2.Flash and system RAM size configuration
3.USB regulator configuration
4.FlexTimer external clock, hardware trigger, and fault source selection
5.UART0 and UART1 receive/transmit source selection/configuration
2.Memory map and register definition
SIM模块包含了很多域，可以为不同的模块选择clock源和分频比
