msm9225 Oki Semiconductor, msm9225 Datasheet - Page 57

• Manufacturer Part Number: msm9225
• Description: Can Controller Area Network Controller
• Manufacturer: Oki Semiconductor

(4) Error states
(a) Types of error states
• There are three types of error states: error active, error passive, and bus OFF.
• Error states are managed by the transmit error counter and the receive error counter.
• Each error state is classified according to the error counter value.
• The error flag that is output differs depending upon whether the error state is a transmit or
• If the value of the error counter is 96 or greater, the bus may be heavily damaged. The bus must
• If only one node is active at startup, even if data is transmit an Ack will not be returned.
• After reset and after the sleep mode wakes up, the error passive state continues until Ack is
• Reception can be performed even if transmission is in the bus OFF state.
(b) Error counter
¡ Semiconductor
Type of error state
Error active
Error passive
Bus OFF
receive operation
be tested for this condition.
Therefore, error frame and data retransmission are repeated. In this case, the bus OFF state will
not be entered. Even if an error state is repeated at the node that transmits messages, the bus
OFF state will not be entered.
received. Regardless of the number of errors that occur, the transmit error counter will be 255.
The error counter is incremented when errors occur and is decremented when transmission or
reception is performed correctly. Timing of the increment or decrement occurs at the 1st bit of
the error flag.
Transmit/Receive
Operation
Transmit
Transmit
Receive
Receive
Error counter value
from 128 to 255
128 or greater
256 or greater
from 0 to 127
—
Active error flag
(6 consecutive "dominant" bits)
Passive error flag
(6 consecutive "recessive" bits)
Communication not possible.
If 11 consecutive "recessive" bits occur 128
times, then when the error counter = 0, the
state can return to error active.
No bus OFF
Type of error flag to be output
MSM9225
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