T5743P3 데이터 시트보기 (PDF) - Atmel Corporation

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T5743P3

UHF ASK/FSK Receiver

Atmel Corporation 

TLim_min = Lim_min ´ TXClk

TLim_max = (Lim_max –1) ´ TXClk

Lim_min and Lim_max are defined by a 5-bit word each within the LIMIT register.

Using above formulas, Lim_min and Lim_max can be determined according to the

required TLim_min, TLim_max and TXClk. The time resolution defining TLim_min and TLim_max is

TXClk. The minimum edge-to-edge time tee (tDATA_L_min, tDATA_H_min) is defined according

to the section ‘Receiving Mode’. The lower limit should be set to Lim_min ³ 10. The

maximum value of the upper limit is Lim_max = 63.

If the calculated value for Lim_min is < 19, it is recommended to check 6 or 9 bits

(NBit-check) to prevent switching to receiving mode due to noise.

Figure 13, Figure 14 and Figure 15 illustrate the bit check for the bit-check limits

Lim_min = 14 and Lim_max = 24. When the IC is enabled, the signal processing circuits

are enabled during TStartup. The output of the ASK/FSK demodulator (Dem_out) is unde-

fined during that period. When the bit check becomes active, the bit-check counter is

clocked with the cycle TXClk.

Figure 13 shows how the bit check proceeds if the bit-check counter value CV_Lim is

within the limits defined by Lim_min and Lim_max at the occurrence of a signal edge. In

Figure 14 the bit check fails as the value CV_lim is lower than the limit Lim_min. The bit

check also fails if CV_Lim reaches Lim_max. This is illustrated in Figure 15.

Figure 13. Timing Diagram During Bit Check

( Lim_min = 14, Lim_max = 24 )

IC_ACTIVE

Bit check ok

Bit check ok

Bit check

Dem_out

Bit-check-

counter

1/2 Bit

1/2 Bit

1/2 Bit

0

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4

TStart-up

Start-up mode

TXClk

TBit-check

Bit-check mode

Figure 14. Timing Diagram for Failed Bit Check (Condition: CV_Lim < Lim_min)

( Lim_min = 14, Lim_max = 24 )

Bit check failed ( CV_Lim < Lim_min )

IC_ACTIVE

Bit check

Dem_out

Bit-check-

counter

1/2 Bit

0

1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12

TStart-up

TBit-check

Start-up mode

Bit-check mode

0

TSleep

Sleep mode

14 T5743

4569A–RKE–12/02

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