SABRE-LL-I datasheet(27/141 Pages) STMICROELECTRONICS

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SABRE-LL-I

Start-up configurations

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Start-up configurations

8.1

Overview

S.A.B.Re start-up configuration is selected by setting in different states the GPIO[0],

GPIO[3] and GPIO[4] pins. Each of these is a three state input pin and is able to distinguish

among the following situations:

Note: “Shorted” means: R

≤1KOhm; “Z” means: R≥10KOhm, C≤200pF

8.2

Operation modes

When VSupply voltage is applied to S.A.B.Re, the internal regulator V3v3, used to supply the

logic circuits inside the device, starts its functionality. When it reaches its final value,

S.A.B.Re enables the GPIO[0] pin state read circuitry, and, after a time TpinSample, it will

sample the GPIO[0] state. If it is found to be in high impedance, S.A.B.Re does not consider

GPIO[3] and GPIO[4] pins state and starts its “Basic device” mode sequence. If GPIO[0] is

found to be connected to ground or to V3v3, S.A.B.Re checks the state of GPIO[3] and

GPIO[4] pins to select its start-up configuration.

The possible configurations can be classified in four “Major” modes:

Basic device.

Slave device.

Master device.

Single device.

Hereafter is reported the correspondence table between GPIO[X] state and S.A.B.Re

configurations.

Table 14.

Possible start-up pins state symbol

Pin condition

State symbol

Shorted to ground

Shorted to V3v3 pin

Floating

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