Texas Instruments Tiva TM4C123GH6PM, User Manual

Page: 200 / 352

System Control
ROM Location:
ROM_APITABLE
is an array of pointers located at
0x0100.0010
.
ROM_SYSCTLTABLE
is an array of pointers located at
ROM_APITABLE[13]
.
ROM_SysCtlClockGet
is a function pointer located at
ROM_SYSCTLTABLE[24]
.
Description:
This function determines the clock rate of the processor clock. This is also the clock rate of all
the peripheral modules (with the exception of PWM, which has its own clock divider).
Note:
This will not return accurate results if ROM_SysCtlClockSet() has not been called to configure
the clocking of the device, or if the device is directly clocked from a crystal (or a clock source)
that is not one of the supported crystal frequencies. In the later case, this function should be
modified to directly return the correct system clock rate.
Returns:
The processor clock rate.
18.2.1.4 ROM_SysCtlClockSet
Sets the clocking of the device.
Prototype:
void
ROM_SysCtlClockSet(uint32_t ui32Config)
ROM Location:
ROM_APITABLE
is an array of pointers located at
0x0100.0010
.
ROM_SYSCTLTABLE
is an array of pointers located at
ROM_APITABLE[13]
.
ROM_SysCtlClockSet
is a function pointer located at
ROM_SYSCTLTABLE[23]
.
Parameters:
ui32Config is the required configuration of the device clocking.
Description:
This function configures the clocking of the device. The input crystal frequency, oscillator to be
used, use of the PLL, and the system clock divider are all configured with this function.
The ui32Config parameter is the logical OR of several different values, many of which are
grouped into sets where only one can be chosen.
The system clock divider is chosen with one of the following values: SYSCTL_SYSDIV_1 ,
SYSCTL_SYSDIV_2 , SYSCTL_SYSDIV_3 , ... SYSCTL_SYSDIV_64 .
The use of the PLL is chosen with either SYSCTL_USE_PLL or SYSCTL_USE_OSC .
The external crystal frequency is chosen with one of the following val-
ues: SYSCTL_XTAL_1MHZ , SYSCTL_XTAL_1_84MHZ , SYSCTL_XTAL_2MHZ ,
SYSCTL_XTAL_2_45MHZ , SYSCTL_XTAL_3_57MHZ , SYSCTL_XTAL_3_68MHZ ,
SYSCTL_XTAL_4MHZ , SYSCTL_XTAL_4_09MHZ , SYSCTL_XTAL_4_91MHZ ,
SYSCTL_XTAL_5MHZ , SYSCTL_XTAL_5_12MHZ , SYSCTL_XTAL_6MHZ ,
SYSCTL_XTAL_6_14MHZ
,
SYSCTL_XTAL_7_37MHZ
,
SYSCTL_XTAL_8MHZ
,
SYSCTL_XTAL_8_19MHZ
,
SYSCTL_XTAL_10MHZ
,
SYSCTL_XTAL_12MHZ
,
SYSCTL_XTAL_12_2MHZ , SYSCTL_XTAL_13_5MHZ , SYSCTL_XTAL_14_3MHZ ,
200 April 8, 2013