Motorola MCF5282, MCF5281 Software Watchdog Timer, Phase Locked Loop PLL, DMA Controller, Reset

MCF5282 Key Features

1.1.14 Software Watchdog Timer

The watchdog timer is a 16-bit timer that facilitates recovery from runaway code. The watchdog counter is a free-running down-counter that generates a reset on underflow. To prevent a reset, software must periodically restart the countdown.

1.1.15 Phase Locked Loop (PLL)

The clock module contains a crystal oscillator (OSC), phase-locked loop (PLL), reduced frequency divider (RFD), status/control registers, and control logic. To improve noise immunity, the PLL and OSC have their own power supply inputs, VDDPLL and VSSPLL. All other circuits are powered by the normal supply pins, VDD and VSS.

1.1.16 DMA Controller

The Direct Memory Access (DMA) controller module provides an efficient way to move blocks of data with minimal processor interaction. The DMA module provides four channels (DMA0–DMA3) that allow byte, word, longword or 16-byte burst line transfers. These transfers are triggered by software, explicitly setting a DCRn[START] bit or the occurrence of a hardware event from one of the on-chip peripheral devices, such as a capture event or an output reference event in a DMA timer (DTIMn) for each channel. The DMA controller supports dual-address mode to on-chip devices.

1.1.17 Reset

The reset controller is provided to determine the cause of reset, assert the appropriate reset signals to the system, and keep track of what caused the last reset. The power management registers for the internal low-voltage detect (LVD) circuit are implemented in the reset module. There are seven sources of reset:

•External

•Power-on reset (POR)

•Watchdog timer

•Phase-locked loop (PLL) loss of lock

•PLL loss of clock

•Software

•Low-voltage detection (LVD) reset

External reset on the RSTO pin is software-assertable independent of chip reset state. There are also software-readable status flags indicating the cause of the last reset, and LVD control and status bits for setup and use of LVD reset or interrupt.

1-14 MCF5282 User’s Manual MOTOROLA