STV3550 datasheet(86/144 Pages) STMICROELECTRONICS

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STV3550

TV Chassis Control

The STV3550 includes the following peripherals for TV chassis control:

●

30 fully-programmable I/Os

●

4 external interrupts

●

8-bit programmable PWM with 4 inputs/outputs

●

Infrared Digital Preprocessor

●

Real Time Clock and Watchdog Timer

●

4 16-bit basic timers

●

10-bit ADC with 6 inputs and wake-up capability

●

2 Master/Slave I²C Bus Interface

●

UART and support for IrDA interfaces

7.1

PWM and Counter Module

This module contains two separate functions:

●

Pulse Width Modulation (PWM) decoder linked to 4 PWM outputs,

●

a 32-bit counter with 4 input capture and compare capabilities.

7.1.1

External Interface

7.1.2

PWM Functions

The pulse width signal generator is used for the digital generation of up to 4 analog outputs when

used with an external filtering network.

The unit, based on a unique 8-bit free-running counter clocked by the 27 MHz clock, can be

prescaled by a 4-bit prescaler and provide frequencies from 6591.8 Hz up to 105468.75 Hz. Four 8-

bit comparators are used to select 4 aspect ratios for the same PWM frequency. The period of the

four 8-bit PWMs is therefore identical and synchronized.

The four PWM outputs must be configured as Alternate function output push-push or open drain.

An interrupt can be generated at the counter overflow.

When the PWM counter starts, the output is set to 1. When the counter matches the PWM compare

value, the output is reset to 0. The output will return to 1 when the counter overflows.

Table 22: Parallel Input/Output Pins

Pin No.

Pin Name

Main Function

(after Reset)

Alternate Function

131

PORTA0

Port A0

PWMCAPTURE0/PWM0

133

PORTA1

Port A1

PWMCAPTURE1/PWM1

PORTA2

Port A2

PWMCAPTURE2/PWM2

PORTA3

Port A3

PWMCAPTURE3/PWM3

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