Functions; Determining Bus Priority; Bit Stuffing; Table 16-9: Determining Bus Priority - NEC V850E/RS1 User Manual

16.3 Functions

16.3.1 Determining bus priority

(1) When a node starts transmission:
During bus idle, the node that output data first transmits the data.
(2) When more than one node starts transmission:
The node that consecutively outputs the dominant level for the longest from the first bit of the arbi-
tration field has the bus priority (if a dominant level and a recessive level are simultaneously trans-
mitted, the dominant level is taken as the bus value).
The transmitting node compares its output arbitration field and the data level on the bus.
(3) Priority of data frame and remote frame
When a data frame and a remote frame are on the bus, the data frame has priority because its
RTR bit, the last bit in the arbitration field, carries a dominant level.
Caution:

16.3.2 Bit stuffing

Bit stuffing is used to establish synchronization by appending 1 bit of inverted-level data if the same
level continues for 5 bits, in order to prevent a burst error.
Transmission
Reception
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Chapter 16 FCAN Controller

Table 16-9: Determining Bus Priority

Level match
Level mismatch
If the extended-format data frame and the standard-format remote frame conflict on
the bus (if ID28 to ID18 of both of them are the same), the standard-format remote
frame takes priority.

Table 16-10: Bit Stuffing

During the transmission of a data frame or remote frame, when the same level continues for 5
bits in the data between the start of frame and the ACK field, 1 inverted-level bit of data is
inserted before the following bit.
During the reception of a data frame or remote frame, when the same level continues for 5 bits in
the data between the start of frame and the ACK field, reception is continued after deleting the
next bit.
User's Manual U16702EE3V2UD00
Continuous transmission
Continuous transmission
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