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Chapter 11
System Interface Unit
110
110
The system interface unit (SIU) controls system startup, initialization and operation,
protection, as well as the external system bus. The system conÞguration and protection
function controls the overall system and provides various monitors and timers, including
the bus monitor, software watchdog timer, periodic interrupt timer (PIT), PowerPCª
decrementer, timebase, and real-time clock. The clock synthesizer generates the clock
signals for other modules and external devices that the SIU interfaces with. The SIU
supports various low-power modes that supply different ranges of power consumption,
functionality, and wake-up time. The clock scheme supports low-power modes for
applications that use baud rate generators and/or serial ports in standby mode. The main
system clock can be changed dynamically; the baud rate generators and serial ports work
with a Þxed frequency. For more information, see Chapter 15, ÒClocks and Power Control.Ó
The external bus interface handles the transfer of information between internal buses and
the memory or peripherals in the external address space. The MPC860 is designed to allow
external bus devices to request and obtain system bus mastership. Chapter 3, ÒHardware
Interface Overview,Ó describes bus operation. The memory controller module provides a
glueless interface to many types of memory devices and peripherals; it supports a maximum
of eight memory banks, each with its own device and timing attributes. Memory control
services are provided to both internal and external masters. The MPC860 supports circuit
board test strategies through user-accessible test logic that is fully compliant with the IEEE
1149.1 standard described in Chapter 38, ÒIEEE 1149.1 Test Access Port.Ó
The PCMCIA host adapter module provides all control logic for a PCMCIA interface. This
interface complies fully with the PCMCIA standard, Release 2.1+ (PC Card -16). It can
support two PCMCIA sockets with a maximum of eight memory or I/O windows.
11.1 Features
The following is a list of the SIUÕs main features:
¥ System conÞguration and protection
¥ System interrupt conÞguration
¥ System reset monitoring and generation
¥ Clock synthesizer
MOTOROLA
Chapter 11. System Interface Unit
11-1
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