CC1110-RTR1 datasheet(90/203 Pages) TI

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CC1110

CC1110 PRELIMINARY Datasheet (Rev. 1.01) SWRS033A

Page 90 of 202

13.3 16-bit Timer, Timer 1

Timer 1 is an independent 16-bit timer which

supports typical timer/counter functions such

as input capture, output compare and PWM

functions. The timer has three independent

capture/compare channels. The timer uses

one I/O pin per channel. The timer is used for

a wide range of control and measurement

applications and the availability of up/down

count mode with three channels will for

example allow implementation of motor control

applications.

The features of Timer 1 are as follows:

•

Three capture/compare channels

•

Rising, falling or any edge input

capture

•

Set, clear or toggle output compare

•

Free-running, modulo or up/down

counter operation

•

Clock prescaler for divide by 1, 8, 32

or 128

•

Interrupt request generated on each

capture/compare and terminal count

•

Capture triggered by radio

•

DMA trigger function

13.3.1 16-bit Timer Counter

The timer consists of a 16-bit counter that

increments or decrements at each active clock

edge. The period of the active clock edges is

defined by the register bits CLKCON.TICKSPD

which sets the global division of the system

clock giving a variable clock tick frequency

from 0.203 MHz to 26 MHz. This is further

divided in Timer 1 by the prescaler value set

by T1CTL.DIV. This prescaler value can be

from 1 to 128. Thus the lowest clock frequency

used by Timer 1 is 1586.9 Hz and the highest

is 26 MHz when the 26 MHz crystal oscillator

is used as system clock source. When the 13

MHz RC oscillator is used as system clock

source, then the highest clock frequency used

by Timer 1 is 13 MHz.

The counter operates as either a free-running

counter, a modulo counter or as an up/down

counter for use in centre-aligned PWM.

It is possible to read the 16-bit counter value

through the two 8-bit SFRs; T1CNTH and

T1CNTL, containing the high-order byte and

low-order byte respectively. When the T1CNTL

is read, the high-order byte of the counter at

that instant is buffered in T1CNTH so that the

high-order byte can be read from T1CNTH.

Thus T1CNTL shall always be read first before

reading T1CNTH.

All write accesses to the T1CNTL register will

reset the 16-bit counter.

The counter produces an interrupt request

when the terminal count value (overflow) is

reached. It is possible to clear and halt the

counter with T1CTL control register settings.

The counter is started when a value other than

00 is written to T1CTL.MODE. If 00 is written to

T1CTL.MODE the counter halts at its present

value.

13.3.2 Timer 1 Operation

In general, the control register T1CTL is used

to control the timer operation. The various

modes of operation are described below.

13.3.3 Free-running Mode

In the free-running mode of operation the

counter starts from 0x0000 and increments at

each active clock edge. When the counter

reaches 0xFFFF the counter is loaded with

0x0000 and continues incrementing its value

as shown in Figure 13. When the terminal

count value 0xFFFF is reached, the flag

T1CTL.OVFIF is set. An interrupt request is

generated if the corresponding interrupt mask

bit TIMIF.OVFIM is set. The free-running

mode can be used to generate independent

time intervals and output signal frequencies.

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