AS8221-ASSP datasheet(22/41 Pages) AMSCO

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AS8221

Datasheet - Application In form atio n

www.austriamicrosystems.com/flexray/AS8221

Revision 1.4

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9.2.2 ERRN Signalling

The ERRN signalling is shown in Table 8.

9.3 Loss of Ground

Whenever a loss of ground is detected, the bus lines are switched Idle_HZ with the precondition that the host pins are open. Either error or no

error can be indicated on the ERRN pin.

9.4 Error Flags

9.4.1 Undervoltage

UVVBAT_DET: The VBAT undervoltage flag is set if the VBAT voltage falls below VBATTHL for longer than tUV_DETECT and is reset if the

VBAT voltage reaches a voltage level higher than VBATTHH for longer than tUV_DETECT.

UVVIO_DET: The VIO undervoltage flag is set if the VCC voltage falls below VCCTHL for longer than tUV_DETECT and is reset if the VCC

voltage reaches a voltage level for longer than VCCTHH after tUV_DETECT.

UVVCC_DET: The VCC undervoltage flag is set if the VIO voltage falls below VIOTHL for longer than tUV_DETECT and is reset if the VIO volt-

age reaches a voltage level higher than VIOTHH for longer than tUV_DETECT.

9.4.2 Bus Error (BUSERR)

The bus error flag is set if 2 consecutive rising edges on the TxD pin without any rising edge on the RxD pin are detected or if 2 consecutive

falling edges on the TxD pin without any falling edge on the RxD pin are detected. This flag is reset if a rising edge on the TxD pin is followed by

a rising edge on RxD pin before the next TxD rising edge or if a falling edge on the TxD pin is followed by a falling edge on RxD pin before the

next TxD falling edge. This flag can be set or reset only in NORMAL mode when the transmitter is enabled. The flag is reset at POWER-OFF.

9.4.3 Short Circuit between BP and BM (BP_BM)

The BP_BM can only be set or reset in NORMAL mode while the driver is active (edge at TxEN) for a time longer than tBUS_ERROR.

The flag is set if the absolute value of the differential voltage is lower than VSHORT for a time tBUS_ERROR.

The flag is reset in POWER-OFF mode and if the set condition is not fulfilled.

9.4.4 Over Temperature (OT)

This flag can only be set or reset in the non-low-power modes. The flag is set if the junction temperature exceeds OTTH and it is reset if the

junction temperature falls below OTTL.

9.4.5 TxEN_BGE Timeout (TxEN_TO)

This flag can only be set in NORMAL mode if the driver is enabled (TxEN is low and BGE is high) for a time longer than tTxEN_max. It is reset

during transition on TxEN or BGE or if the device exits NORMAL mode. If the flag is set the driver is disabled.

Table 8. ERRN Signalling

Supply Voltage Flag Event

VIO

RWAKE Flag

LWAKE Flag

Host Command

ERRN

STBN

NOT [error flag]

If rising edge at EN, then

NOT [error flag] else L

If rising edge at EN, then

NOT [error flag] else H

→HL

→L

→HL

→L

→HL

→HH

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