NCV7341
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8
Table 4. INTERNAL FLAGS AND THEIR VISIBILITY
Internal Flag
Set Condition
Reset Condition
Visibility on Pin ERR
VCC/VIO Undervoltage
VCC < VCC(SLEEP) longer than tUV(VCC)
or VIO < VIO(SLEEP) longer than tUV(VIO)
At wakeup or powerup
No
VBAT Undervoltage
VBAT < VBAT(STB)
When VBAT recovers
No
Powerup
VBAT rises above VBAT(PWUP)
(VBAT connection to the transceiver)
When normal mode is
entered
In receiveonly mode. Not
going from normal mode
Wakeup
When remote or local wakeup is
detected
At powerup or when normal
mode is entered or when
VCC/VIO undervoltage flag is
set
Both on ERR and RxD (both
pulled to low). In
gotosleep, standby and
sleep mode.
Local Wakeup
When local wakeup is detected
(i.e.via pin WAKE)
At powerup or when leaving
normal mode
In normal mode before 4
consecutive dominant
symbols are sent. Then ERR
pin becomes High again
Failure
Pin TxD clamped low or
overtemperature
When entering normal mode
or when RxD is Low while
TxD is high (provided all
failures disappeared)
Overtemperature condition
observable in receiveonly
mode entered from normal
mode
Bus Failure
(NCV7341D20)
One of the bus lines shorted to ground
or supply during four consecutive
transmitted dominants
No bus line short (to ground
or supply) detected during
four consecutive dominant bit
transmissions
In normal mode
VCC/VIO Undervoltage Flag
The VCC/VIO undervoltage flag is set if VCC supply drops
below VCC(sleep) level for longer than tUV(VCC) or VIO
supply drops below VIO(sleep) level for longer than tUV(VIO).
If the flag is set, the transceiver enters sleep mode. After a
waiting time identical to the undervoltage detection times
tUV(VCC) and tUV(VIO), respectively, the flag can be reset
either by a valid wakeup request or when the powerup flag
is set. During this waiting time, the wakeup detection is
blocked.
VBAT Undervoltage Flag
The flag is set when VBAT supply drops below VBAT(STB)
level. The transceiver will enter the standby mode. The flag
is reset when VBAT supply recovers. The transceiver then
enters the mode defined by inputs STB and EN.
Powerup Flag
This flag is set when VBAT supply recovers after being
below VBAT(PWUP) level, which corresponds to a
connection of the transceiver to the battery. The VCC/VIO
undervoltage flag is cleared so that the transceiver cannot
enter the Gotosleep Mode, ensuring that INH Pin is high
and the external voltage regulators are activated at the
battery connection. In Receiveonly mode, the powerup
flag can be observed on the ERR Pin. The flag is reset when
Normal mode is entered.
Wakeup Flag
This flag is set when the transceiver detects a valid
wakeup request via the bus or via the WAKE Pin. Setting
the wakeup flag is blocked during the waiting time of the
VCC/VIO undervoltage flag. The wakeup flag is
immediately propagated to Pins ERR and RxD – provided
that supplies VCC and VIO are available. The wakeup flag
is reset at powerup or when VCC/VIO undervoltage occurs
or when Normal mode is entered.
Local wakeup Flag
This flag is set when a valid wakeup request through
WAKE Pin occurs. It can be observed on the ERR Pin in
normal mode. It can only be set when the powerup flag is
reset. The local wakeup flag is reset at powerup or at
leaving Normal mode.
Failure Flag
The failure flag is set in one of the following situations:
TxD Pin is Low (i.e. dominant is requested by the CAN
controller) for longer than tdom(TxD) Under this
condition, the transmitter is disabled so that a bus
lockup is avoided in case of an application failure
which would drive permanent dominant on the bus. The
transmitter remains disabled until the failure flag is
reset.
Overtemperature If the junction temperature reaches
TJ(SD), the transmitter is disabled in order to protect it
from overheating and the failure flag is set. The
transmitter remains disabled until the failure flag is
reset.
The failure flag is reset when Normal mode is entered or
when TxD pin is High while RxD pin is Low. In case of
overtemperature, the failure flag is observable on pin ERR.
Bus Failure Flag (NCV7341D20)
The transmitter of the NCV7341D20 device version
allows bus failure detection. During dominant bit
transmission, a short of the CANH or CANL line to ground
or supply (VCC, VBAT or other) is internally detected. If the
short circuit condition lasts for four consecutive dominant