The TCAN146x-Q1 has
several operating modes: normal, standby, listen, sleep and fail-safe mode and two
protected modes. The first four mode selections are made by the SPI register,
8h10[2:0]. Fail-safe mode if enabled is entered due to various fault conditions. The
protected modes are a modified standby modes used to protect the device or bus when
fail-safe mode is disabled. The TCAN146x-Q1 automatically
goes from sleep to standby mode when receiving a WUP or LWU event. When selective
wake is enabled,
the device looks for a wake-up frame (WUF) after receiving a WUP. If a WUF is not
received the device transitions back to sleep mode. See Table 8-1 for the various
modes and what parts of the device are active during each mode.
The TCAN146x-Q1 state
diagram figure, see Figure 8-10, Figure 8-11.
Table 8-1 Mode OverviewBlock | Normal | Standby | Listen | Sleep | Fail-safe | UVIO Protected (Fail-safe Disabled) | TSD Protected (Fail-safe Disabled) |
---|
nINT (If Enabled) | On | On | On | Off | Fault Determines | Off | On |
INH | On | On | On | Off | On | On | On |
LIMP (If Enabled): TCAN1469-Q1 | On if WD fail or Previous mode's state until
cleared | On if WD fail or Previous mode's state
until cleared | Previous mode's state until cleared | Previous mode's state until cleared | On | Previous mode's state until cleared | Previous mode's state until
cleared |
WAKE | Off | On | Off | On | See Note | Off | Off |
SPI | On | On | On | On if VIO present | Fault Determines | Off | On |
Watchdog (if enabled): TCAN1469-Q1 | On | On | Off | Off | Off | Off | Off |
Low Power CAN RX | Off | On | Off | On | On | On | On |
CAN Transmitter | On | Off | Off | Off | Off | Off | Off |
CAN Receiver | On | Off | On | Off | Off | Off | Off |
Note: Fail-safe mode has several blocks that state Fault Determines. The following provides an explanation.
- nINT and SPI can be active if the fault condition is UVCC or TSD. These blocks are off if the fault condition is UVIO.
- INH (default) in fail-safe mode is on, so the processor has power and can read which fault has occurred. When using the fail-safe counter after programmed number of wake up and go back to fail-safe cycles INH can be programmed to turn off and then on.
- The low power CAN (WUP) receiver is powered off of VSUP. A
UVSUP event causes this receiver to be off.
- Once the fail-safe counter limit has been reached and if register 8’h17[6:4] =
100b, FS_CNTR_ACT, the device enters sleep mode and not respond to wake
request. A hard reset (power cycle) is required to bring the device back to
normal operation.
- In fail-safe mode, the SWE timer (if enabled) starts and wake events are
ignored until the fault is cleared. Once fault is cleared the WAKE pin is
active.
- If enabled and the SWE timer times out, the device
enters Sleep mode. This can happen even if faults are cleared and if
no wake event has taken place or the device hasn't had SPI
communication like changing modes.
- During an UVCC event the CAN transmitter and receiver are off and
low power CAN receiver is on.
Note: Notes for all Three Device State Diagrams
- Standby Mode Note (STBY Note)
- When entering from Sleep mode, Fail-safe mode or
from a power up case the SWE timer starts.
- A mode change or clearing interrupts must take place prior to the SWE timer expiring.
- Fail-safe Mode Notes (FSM Note)
- To come out of Fail-Safe Mode the fault must be cleared.
- A wake event must take place and enters Standby
or
- A SPI write can change to any state as long as faults are cleared.
- If enabled, the SWE timer starts upon entering
Fail-safe mode.
- If the SWE
timer times out the device enters Sleep mode.
- The device
still enters Sleep mode if SWE timer times out and faults
clear if no wake event takes place.
- Protected State Notes
- UVIO Protected status happens when the IO voltage
rail that the device is aligned to is removed. This can cause a
mismatch between the device and the processor If timer times out and
UVIO = 1 the device goes to sleep.
- If a Thermal Shutdown and UVIO event take place
at the same time the device enters sleep mode.
- A UVSUP enters
UVSUP mode and once VSUP > UVSUPR
the device enters standby mode except for when this takes place in sleep
mode. In sleep mode the device returns to sleep mode.
Note: For the state diagrams by default, SPI is off in
sleep mode. If VIO is present SPI works in sleep mode but at a
reduced data rate, which includes selective wake sub state as shown in Figure 8-12.