ATA5811 ATMEL Corporation, ATA5811 Datasheet - Page 53

• Manufacturer Part Number: ATA5811
• Description: Ata5811 Uhf Ask/fsk Transceiver
• Manufacturer: ATMEL Corporation

11.1.4
11.1.5
Figure 11-3. Timing Diagram for Complete Successful Bit-check (Number of Checked Bits: 3)
4689F–RKE–08/06
RX_ACTIVE
Bit-check Mode
Configuration the Bit-check
Demod_Out
Bit check
Start-up mode
T
Startup_Sig_Proc
In Bit-check mode the incoming data stream is examined to distinguish between a valid signal
from a corresponding transmitter and signals due to noise. This is done by subsequent time
frame checks where the distance between 2 signal edges are continuously compared to a pro-
grammable time window. The maximum count of this edge to edge test before the transceiver
switches to receiving mode is also programmable.
Assuming a modulation scheme that contains 2 edges per bit, two time frame checks are verify-
ing one bit. This is valid for Manchester, Bi-phase and most other modulation schemes. The
maximum count of bits to be checked can be set to 0, 3, 6 or 9 bits via the variable N
control register 5. This implies 0, 6, 12 and 18 edge to edge checks respectively. If N
set to a higher value, the transceiver is less likely to switch to receiving mode due to noise. In the
presence of a valid transmitter signal, the Bit-check takes less time if N
value. In RX polling mode, the Bit-check time is not dependent on N
an example where 3 bits are tested successful.
According to
its. If the edge to edge time t
Bit-check limit T
T
Figure 11-4. Valid Time Window for Bit-check
Lim_max
, the Bit-check will be terminated and the transceiver switches to sleep mode.
Figure
1/2 Bit
Demod_Out
Lim_max
11-4, the time window for the Bit-check is defined by two separate time lim-
, the check will be continued. If t
1/2 Bit
ee
Bit check mode
T
is in between the lower Bit-check limit T
1/2 Bit
Bit-check
Bit check ok
T
T
Lim_max
1/2 Bit
Lim_min
t
ee
1/2 Bit
1/f
ee
Sig
is smaller than limit T
ATA5811/ATA5812
1/2 Bit
Bit-check
Receiving mode
Bit-check
Lim_min
.
Figure 11-3
Lim_min
is set to a lower
and the upper
or exceeds
Bit-check
Bit-check
shows
53
in
is