Motorola PowerQUICC II MPC8280 Series Reference Manual page 185

Table 4-1. System Configuration and Protection Functions
Function
System The SIU allows the user to configure the system according to the particular requirements. The functions
configuration include control of parity checking and part and mask number constants.
60x bus Monitors the transfer acknowledge (TA) and address acknowledge (AACK) response time for all bus
monitor accesses initiated by internal or external masters. TEA is asserted if the TA/AACK response limit is
exceeded. This function can be disabled if needed.
Local bus Monitors transfers between local bus internal masters and local bus slaves. An internal TEA assertion
monitor occurs if the transfer time limit is exceeded. This function can be disabled.
Software Asserts a reset or NMI interrupt, selected by the system protection control register (SYPCR) if the
watchdog software fails to service the software watchdog timer for a certain period of time (for example, because
timer software is lost or trapped in a loop). After a system reset, this function is enabled, selects a maximum
time-out period, and asserts a system reset if the time-out is reached. The software watchdog timer can
be disabled or its time-out period may be changed in the SYPCR. Once the SYPCR is written, it cannot
be written again until a system reset. For more information, see Section 4.1.5, "Software Watchdog
Timer."
Periodic Generates periodic interrupts for use with a real-time operating system or the application software. The
interrupt periodic interrupt timer (PIT) is clocked by the timersclk clock, providing a period from 122 µs to
timer (PIT) 8 seconds. The PIT function can be disabled if needed. See Section 4.1.4, "Periodic Interrupt Timer
(PIT)."
Time counter Provides a time-of-day information to the operating system/application software. It is composed of a
45-bit counter and an alarm register. A maskable interrupt is generated when the counter reaches the
value programmed in the alarm register. The time counter (TMCNT) is clocked by the timersclk clock.
See Section 4.1.3, "Time Counter (TMCNT)."
Figure 4-2 is a block diagram of the system configuration and protection logic.
Bus clock/8
timersclk
Bus Clock
timersclk
Figure 4-2. System Configuration and Protection Logic
Many aspects of system configuration are controlled by several SIU module configuration
registers, described in Section 4.3.2, "System Configuration and Protection Registers."
MOTOROLA
Freescale Semiconductor, Inc.
Module
Configuration
Bus
Monitors
Periodic Interrupt
Timer
Software
Watchdog Timer
Time
Counter
Chapter 4. System Interface Unit (SIU)
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System Configuration and Protection
Description
System Reset
Core's MCP
TEA
Interrupt
System Reset
Core's MCP
Interrupt
4-3