STMPE1801 datasheet(20/60 Pages) STMICROELECTRONICS

20 / 60 page

System controller

STMPE1801

20/60

Doc ID 17884 Rev 3

7.2

States of operation

Figure 4.

States of operation

The device has two main modes of operation:

●

Operational mode: This is the mode, whereby normal operation of the device takes

place. In this mode, the main finite state machine (FSM) unit routes 32 kHz clock to all

the device blocks.

●

Hibernate mode: This mode is entered automatically in auto-hibernate mode. When the

device is in Hibernate mode, the 32 kHz clock is disabled. If there is a keypad activity,

interrupt event, hotkey activity or I2C transaction, the device switches to operational

mode. A reset event brings back the system to operational mode.

7.2.1

Auto-hibernate

The STMPE1801 is set to go into Hibernate mode automatically if there is a period of

inactivity (~ 100 µs) following the completion of I2C transaction with the host. The

STMPE1801 will continue counting down for hibernation mode activation even if there is an

I2C transaction sent by the host to other slave devices. Any I2C transaction from the host to

the STMPE1801 resets the hibernate counter.

Auto-hibernate mode occurs only when all the keys are released and FIFO is emptied

through reading. This is to prevent any loss of data.

The hibernate mode counter should start when any of the following conditions is detected:

–

Once the I2C transaction is completed or a STOP condition is detected.

–

If the device ID in the I2C transaction is invalid.

When there is a keypad activity, the device should go into Hibernate mode ONLY when all

the previously pressed keys are released.

AM04176V1

Hibernate

3 2 kH z: O F F

O perational

3 2 kH z: O N

No a c tivity

(~ 100

μs)

Ke yp a d , in te rrupts

& I

C tra nsaction

(~ 48

μs)

Re s et

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