upd70f3422gj-gae-qs-ax Renesas Electronics Corporation., upd70f3422gj-gae-qs-ax Datasheet - Page 659

• Manufacturer Part Number: upd70f3422gj-gae-qs-ax
• Description: 32-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

CAN Controller (CAN)
Caution
(5)
(c) Occurrence of bit error in intermission
An overload frame is generated.
If an error occurs, it is controlled according to the contents of the transmission
error counter and reception error counter before the error occurred. The value
of the error counter is incremented after the error flag has been output.
Recovery from bus-off state
When the CAN module is in the bus-off state, the transmission pins (CTXDn)
cut off from the CAN bus always output the recessive level.
The CAN module recovers from the bus-off state in the following bus-off
recovery sequence.
<1> Request to enter the CAN initialization mode
<2> Request to enter a CAN operation mode
(a) Recovery from bus-off state through normal recovery sequence
The CAN module first issues a request to enter the initialization mode (refer
too timing <1> in Figure 19-17 on page 660). This request will be immediately
acknowledged, and the CnCTRL.OPMODE bit is cleared to 000B. Processing
such as analyzing the fault that has caused the bus-off state, re-defining the
CAN module and message buffer using application software, or stopping the
operation of the CAN module can be performed by clearing the
CnGMCTRL.GOM bit to 0.
Next, the module requests to change the mode from the initialization mode to
an operation mode (refer to timing <2> in Figure 19-17 on page 660). This
starts an operation to recover the CAN module from the bus-off state. The
conditions under which the module can recover from the bus-off state are
defined by the CAN protocol ISO 11898, and it is necessary to detect 11
consecutive recessive-level bits 128 times or more. At this time, the request to
change the mode to an operation mode is held pending until the recovery
conditions are satisfied. When the recovery conditions are satisfied (refer to
timing <3> in Figure 19-17 on page 660), the CAN module can enter the
operation mode it has requested. Until the CAN module enters this operation
mode, it stays in the initialization mode. Whether the CAN module has entered
the operation mode can be confirmed by reading OPMODE.
During the bus-off period and bus-off recovery sequence, the CnINFO.BOFF
bit stays set (to 1). In the bus-off recovery sequence, the reception error
counter (CnERC.REC0 to CnERC.REC6) counts the number of times 11
consecutive recessive-level bits have been detected on the bus. Therefore, the
recovery state can be checked by reading the REC0 to REC6 bits.
Preliminary User’s Manual U17566EE1V2UM00
(a) Recovery operation through normal recovery sequence
(b) Forced recovery operation that skips recovery sequence
Chapter 19
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