T410 datasheet(52/84 Pages) STMICROELECTRONICS

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10 PWM/TIMER

ST52T410/ST52x420 offers three on-chip PWM/

Timer peripherals:TIMER0, TIMER1 and TIMER2.

The ST52T410/ST52x420 timers have the same

internal structure. The timer consists of an 8-bit

counter with a 16-bit programmable prescaler,

giving a maximum count of 224 (see Figure 10.1).

Figure 10.1 Timer Peripheral Block Diagram

Next, the generic timer is called Timer x, where x

canbe0, 1 or 2.

Each timer has two different working modes, which

can be selected by setting the correspondent

TxMODE bits of REG_CONF5, REG_CONF8 and

REG_CONF10 registers: Timer Mode and PWM

(Pulse Width Modulation) Mode.

All Timers have Autoreload Functions in PWM

Mode.

Each

timer

output

available,

with

its

complementary signal on external pins by setting

PAx

and

PCx

bits

REG_CONF12

and

REG_CONF16 (see Table 10.8 and Table 10.9).

Note: In order to enable timer output (TxOUT or

TxOUT) the related pin must be configured in

Output Mode by setting REG_CONF4 and

REG_CONF15 registers (see Table 7.4 and

Table 7.6)

In particular, TIMER0 can also use external

START/STOP signals (Input capture and Output

compare), external RESET signal and external

CLOCK: PA4/T0STRT, PA0/T0RES and PA5/

T0CLK pins.

Note: In order to use T0RST, T0STR, T0CLK

external signals the related pins must be

configured

Input

Mode

setting

REG_CONF4 and REG_CONF7 registers (see

Table 7.4 and Table 10.3)

For each timer, the content of the 8-bit counter is

incremented on the Rising Edge of the 16-bit

prescaler output (PRESCOUT) and it can be read

at any instant of the counting phase, saved in a

location of RAM memory. The PWM/Timer x

Counter value can be read from the Input Register

PWM_x_COUNT (Input Registers 12, 14 or 16.

See Table 2.2).

The PWM/Timer x Status can be read from the

Input Register PWM_x_STATUS (Input Registers

13, 15 or 17. See Table 2.2 and Table 10.10).

10.1 Timer Mode

TimerModeis selectedby fixingthe TxMODE bit

REG_CONF5,

REG_CONF8

and

REG_CONF10 equal to 0 (see Table 10.1, Table

10.4 and Table 10.6).

Each TIMERx requires three signals: Timer Clock

(TMRCLKx), Timer Reset (TxRES) and Timer Start

(TxSTRT) (see Figure 10.1). Each of these signals

can be generated internally, or, only for Timer 0,

externally by setting T0RST, T0STR, T0CLK bits of

REG_CONF7 register.

TMRCLKx is the Prescaler x output, which

increments the Counter x value on the rising edge.

TMRCLKx is obtained from the internal clock

signal (CLKM) or, only for TIMER0, from the

external signal provided on the PA5/T0CLK pin.

BIT0

BIT1

BIT2

BIT3

BIT4

BIT5

BIT14

BIT15

BIT3

BIT0

BIT1

BIT2

BIT6

BIT4

BIT5

BIT7

17- 1MULTIPLEXER

16-BITPRESCALER

8-BITCOUNTER

PRESCx

CLKM

TMRCLK

TxRES

TxSTRT

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