MPXY8300 datasheet(94/164 Pages) FREESCALE

94 / 164 page

MPXY8300 Series

Sensors

Freescale Semiconductor

Figure 12-9 Manchester Datagram Format

12.5.1

Sample Time in Manchester Data Mode

In the Manchester data mode the LFR detector is powered up periodically, tSAMPLE, to sample for signals applied to the LFR

detector. The periodic rate of the sampling, tSAMPLE, is defined as:

In the beginning of tSAMPLE time, LFR decoder turns on the MFO and the LFR detector at the rising edge of the LFO. The LFR

detector and MFO remain turned on during tLFON time.

If LFR detector does not receive a signal greater than the detect threshold during tLFON time, the LFR decoder turns off the LFR

detector and the MFO as shown in the example in Figure 12-10.

During the tLFON time if a signal greater than the detect threshold is received, the LFR detector attempts to acquire the signal

with the automatic gain control (AGC). The LFR detector needs to receive 5 Manchester zeros to acquire the signal and set the

AGC level. This time is referred to as tACQ.

If an error is detected, the module will be placed in a reset state for the duration set by LFS[3:0]. An error may be in the form of:

Carrier frequency out of bounds

Data rate out of bounds

No signal present

2 msec period with no signal acquired

An interrupt signal is not generated for an error. See Figure 12-11 for an example of an error sequence.

If a signal is present during tLFON time, but ends before being acquired, then the LFR decoder will turn off the LFR detector after

a maximum of two LFO cycles.

PREAMBLE

SYNC

WAKE-UP

DATA

9 tDATA

8 or 16 tDATA

8 tDATA

tLFPRE

LFDO

tDATA

0.5 tDATA

1.5 tDATA

3 tDATA

tDATA

2 tDATA

Variable

SAMPLE

LFON

RST

MPXY8300 Datasheet(PDF) 94 Page - Freescale Semiconductor, Inc

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