Rainbow Electronics T5761 - Manual (Page 12)

12
T5760/T5761
4561B–RKE–10/02
Figure 14, Figure 15 and Figure 16 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 T
Startup
. 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 T
XClk
.
Figure 14 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 15 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 16.
Figure 11. Timing Diagram During Bit Check
Figure 12. Timing Diagram for Failed Bit Check (Condition: CV_Lim < Lim_min)
Figure 13. Timing Diagram for Failed Bit Check (Condition: CV_Lim
>
= Lim_max)
Bit check
IC_ACTIVE
Dem_out
Bit-check-
counter
0 2 3 4 5 6 2 4 5 1 7 8 1 3 6 7 8 9 11 12 13 14 10
1/2 Bit
15 16 17 18 1 2 3 4 5 6
( Lim_min = 14, Lim_max = 24 )
7 8 9 10 11 12 13 14 15 1 2 3 4
1/2 Bit 1/2 Bit
Bit check ok Bit check ok
T
XClk
Start-up mode Bit-check mode
T
Start-up
T
Bit-check
Bit check
IC_ACTIVE
Bit-check-
counter
0 2 3 4 5 6 2 4 5 1 1 3 6 7 8 9 11 12 10
1/2 Bit
Start-up mode
0
( Lim_min = 14, Lim_max = 24 )
Sleep mode
Bit check failed ( CV_Lim < Lim_min )
Dem_out
Bit-check mode
T
Start-up
T
Bit-check
T
Sleep
Bit check
IC_ACTIVE
Bit-check-
counter
0 2 3 4 5 6 2 4 5 1 7 3 6 7 8 9 11 12 10
1/2 Bit
Start-up mode
20
( Lim_min = 14, Lim_max = 24 )
Sleep mode
Bit check failed ( CV_Lim >= Lim_max )
13 14 15 16 17 18 19 21 22 23 24 0 1
Dem_out
Bit-check mode
T
Start-up
T
Bit-check
T
Sleep