CC2430-RTR1-F64 datasheet(119/234 Pages) TI

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CC2430

CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A

Page 119 of 232

TxCCTLn where n is the channel number, 0 or

1. The settings include input capture and

output compare modes.

13.6.4 Input Capture Mode

When the channel is configured as an input

capture channel, the I/O pin associated with

that channel is configured as an input. After

the timer has been started, either a rising

edge, falling edge or any edge on the input pin

triggers a capture of the 8-bit counter contents

into the associated capture register. Thus the

timer is able to capture the time when an

external event takes place.

The channel input pins are synchronized to the

internal system clock. Thus pulses on the input

pins must have a minimum duration greater

than the system clock period.

Note: before an I/O pin can be used by the

timer, the required I/O pin must be configured

as a Timer 3/4 peripheral pin as described in

sections 13.1.4.4 and 13.1.4.5 .

The content of the 8-bit capture registers is

read out from registers TxCCn.

When a capture takes place the interrupt flag

corresponding to the actual channel is set.

This is TIMIF.TxCHnIF. An interrupt request

is generated if the corresponding interrupt

mask bit TxCCTLn.IM is set.

13.6.5 Output Compare Mode

In output compare mode the I/O pin associated

with a channel shall be set to an output. After

the timer has been started, the contents of the

counter is compared with the contents of the

channel compare register TxCC0n. If the

compare register equals the counter contents,

the output pin is set, reset or toggled according

to the compare output mode setting of

TxCCTL.CMP1:0. Note that all edges on

output pins are glitch-free when operating in a

given compare output mode.

For simple PWM use, output compare modes

4 and 5 are preferred.

Writing to the compare register TxCC0 does

not take effect on the output compare value

until the counter value is 0x00. Writing to the

compare

TxCC1

takes

effect

immediately.

When a compare occurs the interrupt flag

corresponding to the actual channel is set.

This is TIMIF.TxCHnIF. An interrupt request

is generated if the corresponding interrupt

mask bit TxCCTLn.IM is set.

13.6.6 Timer 3 and 4 interrupts

There is one interrupt vector assigned to each

of the timers. These are T3 (interrupt 11) and

T4 (interrupt 12). An interrupt request is

generated when one of the following timer

events occur:

•

Counter reaches terminal count value.

•

Input capture event.

•

Output compare event

The SFR register TIMIF contains all interrupt

flags for Timer 3 and Timer 4. The register bits

TIMIF.TxOVFIF

and

TIMIF.TxCHnIF,

contains the interrupt flags for the two terminal

count value events and the four channel

compare/capture events, respectively. An

interrupt request is only generated when the

corresponding interrupt mask bit is set. If there

are

other

pending

interrupts,

the

corresponding interrupt flag must be cleared

by the CPU before a new interrupt request can

be generated. Also, enabling an interrupt mask

bit will generate a new interrupt request if the

corresponding interrupt flag is set.

13.6.7 Timer 3 and Timer 4 DMA triggers

There are two DMA triggers associated with

Timer 3 and two DMA triggers associated with

Timer 4. These are the following:

•

T3_CH0 : Timer 3 channel 0 compare

•

T3_CH1 : Timer 3 channel 1 compare

•

T4_CH0 : Timer 4 channel 0 compare

•

T4_CH0 : Timer 4 channel 1 compare

Refer to section 13.2 on page 86 for a

description on use of DMA channels.

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