STFPC320 datasheet(14/78 Pages) STMICROELECTRONICS

14 / 78 page

Functional description

STFPC320

14/78

4.2

Cold boot up

When power is first applied to the system, the STFPC320 will be reset. It will then manage

the power to the main board by bringing the STBY pin to a low level. This will wake-up the

main processor which will assert the READY pin to a high level to indicate to STFPC320 of a

proper boot-up sequence.

If the microprocessor does not assert the READY pin to a high within 10s, the STFPC320

will cut off the power to the Host by asserting the STBY pin. The high level on READY pin

signifies that the processor is ready. After this, the processor can configure the STFPC320

by sending the various I2C commands for configuration of display, RC protocol, RTC display

mapping, hot-keys.

The power-up behavior in 2 conditions is shown in the Figure 4.

Note:

Guard timer is turned off by default upon READY assertion.

If the guard timer is to be kept on during READY high condition, the guard timer registers

must be set accordingly by proper commands through I2C bus.

In this power-up condition, the guard timer is triggered by internal POR pulse.

During power-up, the guard timer value is 10s.

Figure 4.

Power-up behaviour

STFPC320 데이터시트(PDF) 14 Page - STMicroelectronics