TSS463B datasheet(16/59 Pages) ATMEL

16 / 59 page

TSS463B

4102E–AUTO–12/04

Figure 14. Framing Sequences

When the complete SOF sequence has been transmitted or received, the circuit will

start the transmission or reception of the identifier field.

All data on the VAN bus, including the identifier and Frame Check Sum (FCS), are

transmitted using enhanced Manchester code.

In enhanced Manchester code, three NRZ bits are transmitted first followed by one

Manchester bit, then three more NRZ bits followed by one Manchester bit and so on.

Since the high state is recessive and the low state is dominant, the bus arbitration can

be done. If a module wants access to the bus, it must first listen to the bus during one

full End of Frame (EOF) and one full Inter Frame Spacing (IFS) period to determine

whether the bus is free or not (i.e. no dominant states received).

Figure 15. Data Encoding

The IFS is defined to be a minimum of 64 prescaled clock periods. The TSS463B,

accepts an IFS of zero prescaled clocks for the reception only of a SOF sequence.

Once the bus has been determined as being free, the module must, if it is an autono-

mous module, emit an SOF sequence or, if it is a synchronous access module, wait until

it detects a preamble sequence.

VAN BUS

SEQUENCE

VAN BUS

SEQUENCE

NUMBER OF

PRESCALED

CLOCKS

PREAMBLE

START OF FRAME

START

SYNC

END OF

DATA

ACK

END OF FRAME

96 112 128 144 160 176 192

VAN BUS

SEQUENCE

VAN BUS

SEQUENCE

VAN BUS

SEQUENCE

NUMBER OF

PRESCALED

CLOCKS

NRZ 0

NRZ 1

MANCHESTER 0

MANCHESTER 1

TSS463B Datasheet(PDF) 16 Page - ATMEL Corporation

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