Occs Driver Sample Application - Freescale Semiconductor DSP56800E User Manual

5.1.4

OCCS Driver Sample Application

The OCCS driver application is designed for Freescale/Motorola EVMs and is intended to
illustrate the usage of this driver by a real example.
The application shows a static and a dynamic initialization of the OCCS module. The static
initialization is performed by the OCCS_INIT command. See configurable items in appconfig.h,
which are written into the OCCS registers. The dynamic initialization is shown using the
OCCS_SET_CORE_CLOCK command.
The OCCS module offers the possibility to generate an interrupt in the event of loss of clock. This
feature is also demonstrated in this sample application. The loss of clock is simulated by pressing
the IRQA button. After the IRQA button is pressed, a loss of clock interrupt is generated. Inside
the interrupt service routine the CHPMPTRI bit in the PLL Control Register (PLLCR) is set.
Afterwards the user should shut down the chip. Setting the CHPMPTRI bit isolates the charge
pump from the loop filter, allowing the PLL output to drift slowly away. The frequency of the
blinking LED is slowly drifting the same way as the PLL output what can be seen on the
debugging LEDs. The debugging LEDs are driven by the PWM module, which is configured
according to the pwm_demo application.
The OCCS driver application can be found at e.g. {DSP56800E_Quick_Start
Source}\..\sample_applications\MC56F8346EVM\occs_demo directory and consists of the
application project occs_demo.mcp and the source code for the application main.c.
FREESCALE SEMICONDUCTOR Targeting 56F8xxx Platform 5-53