IIS2ICLX datasheet(5/119 Pages) STMICROELECTRONICS

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2.1

Finite state machine

The IIS2ICLX can be configured to generate interrupt signals activated by user-defined motion patterns. To

do this, up to 16 embedded finite state machines can be programmed independently for motion detection and

decoding.

Definition of finite state machine

A state machine is a mathematical abstraction used to design logic connections. It is a behavioral model

composed of a finite number of states and transitions between states, similar to a flow chart in which one can

inspect the way logic runs when certain conditions are met. The state machine begins with a start state, goes to

different states through transitions dependent on the inputs, and can finally end in a specific state (called stop

state). The current state is determined by the past states of the system. The following figure shows a generic

state machine.

Figure 1. Generic state machine

Finite state machine in the IIS2ICLX

The IIS2ICLX works as an accelerometer sensor, generating acceleration output data. It is also possible to

connect an external sensor (an accelerometer, a gyroscope, a pressure sensor, and so forth) by using the sensor

hub feature (mode 2). These data can be used as input of up to 16 programs in the embedded finite state

machine (Figure 2. State machine in the IIS2ICLX).

All 16 finite state machines are independent: each one has its dedicated memory area and it is independently

executed. An interrupt is generated when the end state is reached or when some specific command is performed.

Figure 2. State machine in the IIS2ICLX

ACC [LSB]

EXT. SENSOR (GYRO) [LSB]

(optional)

IIS2ICLX

SIGNAL

CONDITIONING

FSM

FSM Output

IIS2ICLX

Finite state machine

DS13005 - Rev 7

page 5/119

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