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Overview
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
1-13
1.4.14
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.
1.4.15
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.
1.4.16
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.
1.4.17
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.
1.4.18
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.
1.4.19
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.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60