Occs Driver; Introduction; Quick Reference; Occs Frequency Calculation - Freescale Semiconductor DSP56800E User Manual

5.1

OCCS Driver

This section describes the DSP56800E_Quick_Start API for the MC56F83xx and MC56F80xx
OCCS on-chip module. The functionality of the OCCS module itself is described in the
MC56F83xx Peripheral User Manual, 56F8000 Peripheral Reference Manual, 56F802x/3x
Peripheral Reference Manual and 56F800x Peripheral Reference Manual.
5.1.1

Introduction

The On-Chip Clock Synthesis (OCCS) module is available on all 56F800E chips and provides
2X system clock frequency to the system integration module (SIM), which uses it to
generate the various chip clocks
Postscaler, PLL, clock multiplexer and lock detector. The main OCCS module features are:
• possibility to use the PLL to multiply the externally generated clock
• PLL loss-of-lock detector with interrupt capability
• Prescaler to divide the input frequency (on MC56F80xx is prescaler fixed to 1 by hardware)
• Postscaler to divide the PLL output frequency
Note that the OCCS module on certain devices is equipped with internal relaxation oscillator, so
no external clock source is needed. The OCCS module on MC56F80xx devices is capable to
generate 3X system clock, called High Speed Peripheral Clock (HS_PERF), to selected peripheral
modules.
There are differences in the way the OCCS module is controlled on different 56F800E
sub-families. The MC56F83xx, MC56F801x and MC56F802x/3x devices each uses a slightly
different PLL modules. In any case, it is recommended to configure the OCCS statically in the
Graphical Configuration Tool and let the DSP56800E_Quick_Start standard start-up code to
apply the configuration.
The following sections describe the OCCS driver software which provides the low level run-time
API to the OCCS hardware.
5.1.2

Quick Reference

This section defines the terms and formulas used later in Section 5.1.3.
Module base address
of / for
OCCS (PLL_BASE)
5.1.2.1

OCCS frequency calculation

For exact frequency formulas, please see the OCCS documentation in the Peripheral Reference
Manual for each sub-family. Different Peripheral Manuals exist for MC56F83xx, MC56F801x,
MC56F802x/3x and MC56F800x sub-families.
FREESCALE SEMICONDUCTOR
. The main blocks of OCCS are frequency Prescaler,
Table 5-1. OCCS Module Base Address
MC56F800x MC56F801x
0xF160 0xF0F0
Targeting 56F8xxx Platform
MC56F802x/3x MC56F83xx
0xF130 0xF2D0
the
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