UPD78F0890GK(A)-GAJ-AX NEC, UPD78F0890GK(A)-GAJ-AX Datasheet - Page 397

• Manufacturer Part Number: UPD78F0890GK(A)-GAJ-AX
• Description: 8BIT MCU, 128K FLASH, 7K RAM, LQFP
• Manufacturer: NEC

Specifications of UPD78F0890GK(A)-GAJ-AX

• Controller Family/series: UPD78F
• No. Of I/o's: 55
• Ram Memory Size: 7KB
• Cpu Speed: 20MHz
• No. Of Timers: 10
• No. Of Pwm: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 128KB
• Oscillator Type: External, Internal

(5) Recovery from bus-off state
When the CAN module is in the bus-off state, the CAN module permanently sets its output signals (CTxD) to
recessive level.
The CAN module recovers from the bus-off state in the following bus-off recovery sequence.
<1> A request to enter the CAN initialization mode
<2> A request to enter a CAN operation mode
(a) Recovery operation from bus-off state through normal recovery sequence
(a) Recovery operation through normal recovery sequence
(b) Forced recovery operation that skips recovery sequence
The CAN module first issues a request to enter the initialization mode (refer to timing <1> in Figure 16-
17). This request will be immediately acknowledged, and the OPMODE bits of the C0CTRL register are
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 GOM bit to 0.
Next, the user requests to change the mode from the initialization mode to an operation mode (refer to
timing <2> in Figure 16-17). 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. 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 16-17), 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. Completion to be requested operation mode can be confirmed
by reading the OPMODE bits of the C0CTRL register.
During the bus-off period and bus-off recovery sequence, the BOFF bit of the C0INFO register stays set
(to 1). In the bus-off recovery sequence, the reception error counter (REC[6:0]) 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 REC[6:0].
Cautions 1
2. In the bus-off recovery sequence, REC[6:0] counts up (+1) each time 11
When the transmission from the initialization mode to any operation modes is
requested to execute bus-off recovery sequence again in the bus-off recovery
sequence, reception error counter is cleared.
Therefore it is necessary to detect 11 consecutive recessive-level bits 128 times on
the bus again.
consecutive recessive-level bits have been detected.
period, the CAN module can enter the CAN sleep mode or CAN stop mode. To start
the bus-off recovery sequence, it is necessary to transit to the initialization mode
once. However, when the CAN module is in either CAN sleep mode or CAN stop
mode, transition request to the initialization mode is not accepted, thus you have
to release the CAN sleep mode first. In this case, as soon as the CAN sleep mode is
released, the bus-off recovery sequence starts and no transition to initialization
mode is necessary. If the can module detects a dominant edge on the CAN bus
while in sleep mode even during bus-off, the sleep mode will be left and the bus-off
recovery sequence will start.
CHAPTER 16 CAN CONTROLLER
User’s Manual U17554EJ4V0UD
Even during the bus-off
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