tda5255e1 Infineon Technologies Corporation, tda5255e1 Datasheet - Page 68

• Manufacturer Part Number: tda5255e1
• Description: Ask/fsk 434mhz Wireless Transceiver
• Manufacturer: Infineon Technologies Corporation

Confidential
3.7.1
The high time of data is used to measure the frequency of the data signal. For Manchester coding
either the data frequency or half of the data frequency have to be detected corresponding to one
high time or twice the high time of data signal.
A time period of 3*2*T is necessary to decide about valid or invalid data.
Figure 3-33
Example to calculate the thresholds for a given data rate:
- Data signal manchester coded
- Data Rate: 2kbit//s
- f
Then the period equals to
respectively the high time is 0,25ms.
We set the thresholds to +-10% and get: T1= 0,225ms and T2= 0,275ms
The thresholds TH1 and TH2 are calculated with following formulas
Preliminary Specification
clk
= 18,0896 MHz
Frequency Window for Data Rate Detection
Window Counter timing
possible
possible
GATE 1
GATE 2
DATA
TH2
TH1
2
×
T
0
0
=
T2
T1
=
T
=
T2
2kbit/s
T1
×
0
0
1
×
f
f
2*T2
2*T1
clk
4
clk
4
2*T
68
=
1
1
0,5ms
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0
t
t
t
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window_count_timing.wmf
TDA5255 E1
Version 1.1
Application
2002-11-28