AS8221
Data Sheet - Detailed Description
8.3.1 NORMAL Mode
In this mode the Transceiver is able to send and receive data signals on the bus. TxEN and BGE enables and disables the transmission of data
streams. INH1 and INH2 outputs are set high. RxD reflects bus data and bus state. The error-read-out-mechanism is enabled. In NORMAL
mode, the transmitter state can be selected as shown in the Table 5. In case the over-temperature flag is set the Transmitter will be disabled. The
bus wires are terminated to VCC/2 via Receiver input resistances.
Table 5. Transmitter State
BGE
H
TxEN
TxD
H
Transmitter state
Enabled
Bus State
L
L
Data1 (BP is driven high, BM is driven low)
Data0 (BP is driven low, BM is driven High)
Idle (BP and BM are not driven)
H
L
Enabled
X
H
X
X
Disabled
L
X
Disabled
Idle (BP and BM are not driven)
ꢀ
If the differential bus voltage is higher than VBUSActiveHigh or lower than VBUSActiveLow for a time longer than tBUSActivityDetection, then activity
is detected on the bus (Bus = active), RxEN is switched to logical “low” and RxD is released.
ꢀ
ꢀ
ꢀ
If, after the activity detection, the differential bus voltage is higher than VData1, RxD is high.
If, after the activity detection, the differential bus voltage is lover than VData0, RxD is low.
If the absolute differential bus voltage is lower than VBUSActiveHigh and higher than VBUSActiveLow for a time longer than tBUSIdleDetection, then
idle is detected on the bus (Bus = idle), RxEN and RxD are switched to logical “high”
8.3.2 RECEIVE-ONLY Mode
In RECEIVE-ONLY mode the Transmitter is disabled but the Receiver is active.
8.3.3 STANDBY Mode
In this mode the Transceiver is not able to send and receive data signals from the bus, but the wake-up detector is active. The power
consumption is significantly reduced with respect to the non-low-power operation modes. RxD and RxEN, reflects the negation of the wake-up
flag. INH1 is set to high. If wake-up flag is set then INH2 is high, otherwise it is floating. The error-read-out-mechanism is not enabled. The bus
wires are terminated to GND (bus state: Idle_LP).
8.3.4 GO-TO-SLEEP Mode
In this mode the Transceiver has the same behavior as in STANDBY mode but if this mode is selected for a time longer than tSLEEP and the wake
flag is cleared the device enters into the SLEEP mode.
8.3.5 SLEEP Mode
In SLEEP mode only the bus wake and local wake detection is enabled. IN1 and INH2 are floating.
8.4 Non Operating Mode
The AS8221 provides the following non operating mode:
8.4.1 POWER-OFF
In this mode the Transceiver is not able to operate. RxD, RxEN are set to high and ERRN is set to low. INH1 and INH2 are floating. The bus
wires are not connected to GND (bus state: Idle_HZ).
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