MPXY8300 datasheet(95/164 Pages) FREESCALE

95 / 164 page

MPXY8300 Series

Sensors

Freescale Semiconductor

Figure 12-10 LFR Sample Timing - Manchester Data Mode (no signal detected during tLFON)

Figure 12-11 LFR Sample Timing - Manchester Data Mode - data error detected

12.5.2

Preamble

The preamble consists of a sequence of Manchester zeros to signal the start of valid information. This preamble must last a

minimum of the 8 Manchester zeros. It is acceptable if the preamble has more than 8 Manchester zeros.

The preamble ends when the incoming signal active pulse width lasts for 1.5 Manchester data bit times. If the number of the

received Manchester zeros during the preamble (until the 1.5 data sync pulse) is less than tPRE(min), then the incoming signals

are ignored, the LFR detector and MFO are turned off and the decoder is reset for a period of time, tRST.

If the correct bits and preamble time are received the LFR detector and the MFO continue to remain powered up to allow the

synchronization period to be decoded.

The LFR decoder has a time-out mechanism that turns off the LFR detector and MFO for tRST when the LFR decoder receives

only Manchester zeros (in preamble) for an extended time, tTIMEOUT, which is defined by counting 65 rising edges of the LFO

clock. The time-out counter will always be enabled when the module is first enabled and will begin after the signal has been

acquired and valid Manchester data coded zeros are received.

12.5.3

Synchronization

In order for the LFR decoder to synchronize to the upcoming wake-up code, a specific pattern of encoded data must be received

during the synchronization interval which lasts a total of nine (9) bit times. If the synchronization pattern fails to match the correct

one, the LFR detector and the MFO are turned off and the LFR decoder is reset for tRST.

If the correct synchronization is decoded the LFR detector and the MFO remain powered up to allow the wake-up code to be

decoded.

LFO

MFO and

are On

tLFON

tLFON = 200 μsec

tSAMPLE

LFR Detector

tRST

LFDO signal

LFO Clock

error in Manchester Datagram

LFR Detector

and MFO

Enables

tRST

tLFON ~ 2msec

signal being acquired

LF signal

MPXY8300 Datasheet(PDF) 95 Page - Freescale Semiconductor, Inc

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