AN2283 Freescale Semiconductor / Motorola, AN2283 Datasheet - Page 31

• Manufacturer Part Number: AN2283
• Description: Scalable Controller Area Network (MSCAN)
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
Motorola Scalable Controller Area Network (MSCAN) Interrupts
The REC dictates what state the node is going to be in according to the number
of errors. Out of reset, the REC is initialized to 0 by the MSCAN. At this time,
the node will be in the No Warning/Error (Error Active) State. When
96 <= REC < 128 the node is Error Active and in the Receiver Warning State.
When 128 <= REC <= 255 the node is Error Passive and in the Receiver Error
Passive State.
The rules REC follows to adjust its values are:
1. When a receiver detects an error, the REC is increased by one. Except
2. When a receiver detects a dominant [0] bit as the first bit after sending
3. When a node’s receiver is Error Active and detects a Bit Error while
4. A node can tolerate up to seven consecutive dominant [0] bits after
5. After a message is received successfully (without error up to the ACK
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WARNING/ERROR
when the detected error was a Bit Error during the sending of an ACTIVE
Error Flag or an Overload which results in the REC being increased by
eight.
an Error Flag, the REC is increased by eight.
sending an Active Error Flag or an Overload Flag, the REC is increased
by eight.
sending an Error Flag (either Active or Passive). After detecting the 8
consecutive dominant [0] bit and after each sequence of eight additional
consecutive dominant [0] bits, every receiver increases its receive error
count by eight [REC + 8].
slot) and after successfully sending the ACK bit:
–
–
–
ERROR ACTIVE)
(NODE STATE:
The Receive Error Count decreases by one if it was between 1 and
127 [REC – 1 if between 1 and 127]
Or, if the Receive Error Count was zero it stays at zero [REC = 0 no
change]
Or, if the Receive Error Count was greater than 127, then it’ll be set
to a value between 119 and 127
[If REC > 127, then 119 <= REC <= 127]
NO
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Figure 23. Receiver Error Polling Method
96 <= REC <128
REC < 96
ERROR ACTIVE)
(NODE STATE:
RECEIVER
WARNING
128 <= REC < 255
96 <= REC < 128
Error Interrupts Overview
ERROR PASSIVE
RECEIVER
AN2283/D
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