STV3550 datasheet(83/144 Pages) STMICROELECTRONICS

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CPU and System Management Functional Description

STV3550

83/144

Depending on application requirements, tasks such as increasing the operating frequency may be

delayed. Other high priority tasks such as TV chassis control can also be included in the boot

sequence.

6.5.2

Starting The Main Application Program

Once hardware resources are properly configured, the main application program can be

downloaded from Flash to SDRAM so that it can be executed into SDRAM with the best

performances.

Main application programs include the OS/20 kernel, STV3550 video and peripheral resource

management, etc., and is discussed in Software Application Notes.

6.6

Standby Mode

The chip includes a Standby mode used to put the TV chassis in standby. During this mode, the chip

is supplied normally but only the sections used to restart the chip are clocked. The other clocks are

switched off. The clocks used in Standby mode are generated from the 27-MHz crystal oscillator

and divided by the Clock Generator block.

After a wake-up request from the IR receiver or from another interrupt source, the STV3550 restarts

the CPU clock. Then, depending on software controls, the CPU continues the task where it has

stopped and decodes the interrupt source.

Wake-up Interrupt sources can be:

●

a command from the AD input level change

●

a command from the IR detector

●

a command from the Real Time Clock (RTC)

●

4 external interrupts

In Standby mode, only the following blocks are clocked:

●

Infrared Preprocessor

●

Real Time Clock (RTC)

●

Analog-to-Digital Converter (ADC)

In addition to Standby mode, the STV3550 includes various “Low Power” modes.

These modes are performed by reducing the clock frequency for each block, or by switching off the

blocks that are not in use (see Power Off bit or RST_soft reset bit for each block).

STV3550 Datasheet(PDF) 83 Page - STMicroelectronics