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MCF52235 ColdFire Microcontroller Data Sheet, Rev. 10
MCF52235 Family Configurations
Freescale Semiconductor
12
1.2.15
Periodic Interrupt Timers (PIT0 and PIT1)
The two periodic interrupt timers (PIT0 and PIT1) are 16-bit timers that provide interrupts at regular intervals with minimal
processor intervention. Each timer can count down from the value written in its PIT modulus register or can be a free-running
down-counter.
1.2.16
Pulse Width Modulation (PWM) Timers
The MCF52235 has an 8-channel, 8-bit PWM timer. Each channel has a programmable period and duty cycle as well as a
dedicated counter. Each of the modulators can create independent continuous waveforms with software-selectable duty rates
from 0 to 100%. The PWM outputs have programmable polarity and can be programmed as left-aligned outputs or
center-aligned outputs. For higher period and duty cycle resolution, each pair of adjacent channels ([7:6], [5:4], [3:2], and [1:0])
can be concatenated to form a single 16-bit channel. The module can, therefore, be configured to support 8/0, 6/1, 4/2, 2/3, or
0/4 8-/16-bit channels.
1.2.17
Software Watchdog Timer
The watchdog timer is a 32-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.
1.2.18
Phase Locked Loop (PLL)
The clock module contains a crystal oscillator, 8 MHz on-chip relaxation oscillator (OCO), phase-locked loop (PLL), reduced
frequency divider (RFD), low-power divider status/control registers, and control logic. To improve noise immunity, the PLL,
crystal oscillator, and relaxation oscillator have their own power supply inputs: VDDPLL and VSSPLL. All other circuits are
powered by the normal supply pins, VDD and VSS.
1.2.19
Interrupt Controller (INTC0/INTC1)
There are two interrupt controllers on the MCF52235. These interrupt controllers are organized as seven levels with up to nine
interrupt sources per level. Each interrupt source has a unique interrupt vector, and provide each peripheral with all necessary
interrupts. Each internal interrupt has a programmable level [1-7] and priority within the level. The seven external interrupts
have fixed levels/priorities.
1.2.20
DMA Controller
The direct memory access (DMA) controller provides an efficient way to move blocks of data with minimal processor
intervention. It has four channels that allow byte, word, longword, or 16-byte burst line transfers. These transfers are triggered
by software explicitly setting a DCRn[START] bit or by the occurrence of certain UART or DMA timer events.
1.2.21
Reset
The reset controller determines the source of reset, asserts the appropriate reset signals to the system, and keeps track of what
caused the last reset. There are seven sources of reset:
External reset input
Power-on reset (POR)
Watchdog timer
Phase locked-loop (PLL) loss of lock
PLL loss of clock
Software