MC68331CEH16 Datasheet, PDF (14/84 Pages) Freescale Semiconductor, Inc – 32-Bit Modular Microcontroller

Freescale Semiconductor, Inc.
3 System Integration Module
The system integration module (SIM) consists of five functional blocks that control system start-up, ini-
tialization, configuration, and external bus.
SYSTEM CONFIGURATION
CLOCK SYNTHESIZER
SYSTEM PROTECTION
XTAL
CLKOUT
EXTAL
MODCLK
CHIP SELECTS
CHIP SELECTS
EXTERNAL BUS INTERFACE
EXTERNAL BUS
RESET
FACTORY TEST
TSC
FREEZE/QUOT
300 S(C)IM BLOCK
Figure 5 SIM Block Diagram
3.1 Overview
The system configuration and protection block controls MCU configuration and operating mode. The
block also provides bus and software watchdog monitors.
The system clock generates clock signals used by the SIM, other IMB modules, and external devices.
In addition, a periodic interrupt generator supports execution of time-critical control routines.
The external bus interface handles the transfer of information between IMB modules and external ad-
dress space.
The chip-select block provides eleven general-purpose chip-select signals and a boot ROM chip-select
signal. Both general-purpose and boot ROM chip-select signals have associated base address regis-
ters and option registers.
The system test block incorporates hardware necessary for testing the MCU. It is used to perform fac-
tory tests, and its use in normal applications is not supported.
The SIM control register address map occupies 128 bytes. Unused registers within the 128-byte ad-
dress space return zeros when read. The “Access” column in the SIM address map below indicates
which registers are accessible only at the supervisor privilege level and which can be assigned to either
the supervisor or user privilege level, according to the value of the SUPV bit in the SIMCR.
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