MCP25020ISLASHP datasheet(7/66 Pages) MICROCHIP

7 / 66 page

DS21664D-page 7

MCP2502X/5X

TEC - TRANSMITTER ERROR COUNTER

REC - RECEIVER ERROR COUNTER

FIGURE 2-3:

BIT TIME PARTITIONING

2.4

Bit Timing Logic

The Bit Timing Logic (BTL) monitors the bus line input

and handles the bus-related bit timing based on the

CAN protocol. The BTL synchronizes on a recessive-

to-dominant bus transition at Start-of-Frame (hard

synchronization) and on any further recessive-to-

dominant bus line transition if the CAN controller itself

does not transmit a dominant bit (resynchronization).

The BTL also provides programmable time segments

to compensate for the propagation delay time, phase

shifts and to define the position of the sample point

within the bit time. These programmable segments are

made up of integer units called Time Quanta (TQ). The

nominal bit time is calculated by programming the TQ

length and the number of TQ in each time segment, as

discussed below.

2.4.1

TIME QUANTUM (TQ)

Time Quantum is a fixed unit of time derived from the

oscillator period. There is a programmable baud rate

prescaler (BRP) (with integral values ranging from 1 to

64) as well as a fixed division by two for clock

generation.

R-0

TEC7

TEC6

TEC5

TEC4

TEC3

TEC2

TEC1

TEC0

bit 7

bit 0

bit 7-0

TEC7:TEC0: Transmit Error Counter bits

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

R-0

REC7

REC6

REC5

REC4

REC3

REC2

REC1

REC0

bit 7

bit 0

bit 7-0

REC7:REC0: Receive Error Counter bits

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

Input Signal

Sync

Prop

Segment

Phase

Segment 1

Phase

Segment 2

Sample Point

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