TLE4943C datasheet(20/48 Pages) INFINEON

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TLE4943C

Data Sheet

V 1.2, July 2018

2.7.6

Bit Stump Suppression

The suppression of bit stumps in the wheel speed sensor (WSS) is implemented and described in this paragraph.

Following principle is used to realize a bit stump suppression:

Constant time shift of output of speed pulse and data protocol:

The sensor output is always completely shifted by a bit time tp when a new protocol starts. This is equivalent to a

time output offset, which has the following effect:

The initial bit is not started immediately at the moment in which a new protocol starts, what could occur during an

ongoing data protocol at high speed. Instead, tp is always initially waited for a time offset within which the last

ongoing protocol output is monitored. For the case a bit output is still active, this will be completely transferred

without being cut off. This will effectively prevent the occurrence of bit stumps. Within this offset time tp,

suppression of the next possible data bit of the last protocol will be introduced. In this way a current bit transfer

will be completed and the transfer of any further bits (of the last protocol) will be prevented. At the end of this offset

time, the transfer of the initial bit will start. Advantage of this procedure: it is also effective in the standstill protocol,

i.e. if a new increment of the encoder is detected during an ongoing standstill protocol, a current ongoing bit

transfer are not be ended in any "bit stump". The transmission of additional bits is suppressed. After delay phase,

the new transfer begins with the initial bit tp/2, followed by speed pulse and data protocol.

The following figures show the effect of the bit stump suppression according to the method described above using

3 representative cases.

1st case: No cutting off of the preceding protocol. The time between two consecutive protocols is sufficient to

transfer all bits. Nevertheless, the new protocol begins at the moment of a new increment of the encoder with the

constant-time output offset of the length tp. This is followed by the initial bitwidth tp/2, then the speed pulse, etc.

Figure 14

Case 1 - No cutting of the preceding protocol

Zero crossing

Subsequent

protocol

Preceding protocol

Initial bit

bit0

bit5

bit4

bit3

bit2

bit1

bit7

bit6

Parity

bit0

bit3

bit2

bit1

Time output offset

tp/2

bit4

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