Bit Timing - Intel 8XC196K Series User Manual

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8XC196K x , J x , CA USER'S MANUAL

12.3.5 Bit Timing

A message object consists of a series of bits transmitted in consecutive bit times. The CAN pro-

tocol specifies a bit time composed of four separate, nonoverlapping time segments: a synchro-

nization delay segment, a propagation delay segment, and two phase delay segments (Figure 12-4

and Table 12-8). The CAN controller implements a bit time as three segments, combining

PROP_SEG and PHASE_SEG1 into t

identical to that of the 82527 CAN peripheral.

Figure 12-4. A Bit Time as Specified by the CAN Protocol

The synchronization delay segment allows for synchronization of the various nodes on

the bus. An edge is expected to lie within this segment.

The propagation delay segment compensates for the physical delay times within the

network. It is twice the sum of the signal's propagation time on the bus line, the input

comparator delay, and the output driver delay. The factor of two accounts for the

requirement that all nodes monitor all bus transmissions for errors.

PHASE_SEG1 This segment compensates for edge phase errors. It can be lengthened or shortened by

resynchronization.

PHASE_SEG2 This segment compensates for edge phase errors. It can be lengthened or shortened by

resynchronization.

(Figure 12-5 and Table 12-9). This implementation is

Nominal Bit Time

Table 12-8. CAN Protocol Bit Time Segments