AS8221-ASSP datasheet(19/42 Pages) AMSCO

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AS8221

Datasheet - Application In form atio n

www.austriamicrosystems.com/flexray/AS8221

Revision 1.7

19 - 42

9.1 Fail Silent Behavior

9.1.1 RxEN / BGE timeout

In case no edges on RxEN and BGE within tTxEN_timeout are detected, the transmitter will stop transmitting the signals on RxD to the bus pins.

9.1.2 State Transitions due to Undervoltage Detection



In case of VBAT or VIO undervoltage is detected, SLEEP mode will be entered regardless the status of EN and STBN.



In case VCC undervoltage is detected, STANDBY mode will be entered regardless the status of EN and STBN.



VBAT and VIO undervoltage detection have higher priority than VCC undervoltage detection.



In case undervoltage at VBAT and VCC is detected, POWER-OFF mode is entered (bus state: Idle_HZ).

9.1.3 State Transitions due to Voltage Recovery Detection



If the voltage recovers the device will enter the mode selected by the EN and STBN pins, in case no undervoltage is present at the other

supply pins.



Starting from the POWER-OFF, the device enters the state selected by the host input pins (EN, STBN) only if VBAT or VCC recovers (VBAT

VBATTHH or VCC VCCTHH) while VIO is available (undervoltage flag of VIO flag not set). If the VIO undervoltage flag is set, the STANDBY

mode will be entered. In both cases the Power-On flag is set.



If VBAT

 VBATTHL and VCC  VCCTHL the device will be in POWER-OFF state, thus the bus wires are not terminated (bus state: Idle_HZ).

9.2 Mode Transitions

In case of power-off event, the device enters POWER-OFF regardless VIO undervoltage flag, wake-up flags and regardless the selection at the

host input pins.

Starting from the POWER-OFF the device enters STANDBY only in case a power on event occurs.

Starting from every operating mode the device enters SLEEP in case VBAT or VIO undervoltage flag is set regardless the VCC undervoltage flag,

the wake-up flag and the state of the host input pins.

Starting from every operating mode except SLEEP the device enters STANDBY in case VCC undervoltage flag is set and VBAT and VIO

undervoltage flags are not set, regardless the wake-up flag indication and the host input pins state.

Starting from a low-power mode the device enters the operation mode indicated by the host input pins if a wake-up event occurs.

In case all the undervoltage flags are reset the operation mode is selected by the wake-up flag and the host pins according to Table 6.

Where:

H = Digital level high, L = Digital level low, X = Do not care!, Floating = The analog output is not driven.

Table 6. Pin Signalling and Operating Modes

Inputs

Operation Mode

OutPut

STBN

RxD

ERRN

RxEN

INH1

INH2

NORMAL

Bus = Data_0

NOT [Error flag]

Bus = Active

Bus = Idle or Data_1

Bus = Idle

RECEIVE-ONLY

Bus = Data_0

NOT [Error flag]

Bus = Active

Bus = Idle or Data_1

Bus = Idle

GO-TO-SLEEP

NOT [Wake-up flag]

Floating

STANDBY

NOT [Wake-up flag]

Floating

SLEEP

NOT [Wake-up flag]

Floating

POWER-OFF

Floating

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