ATA5423-PLSW datasheet(56/100 Pages) ATMEL

56 / 100 page

4841D–WIRE–10/07

ATA5423/ATA5425/ATA5428/ATA5429

9.1.4

Bit-check Mode

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.

9.1.5

Configuration of the Bit Check

Assuming a modulation scheme that contains 2 edges per bit, two time frame checks verify 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

Bit-check in control

Bit-check is set to a

higher value, the transceiver is less likely to switch to receiving mode due to noise. In the pres-

ence of a valid transmitter signal, the bit check takes less time if N

Bit-check is set to a lower value.

In RX polling mode, the bit-check time is not dependent on N

Bit-check if no valid signal is present.

Figure 9-3 shows an example where 3 bits are tested successfully.

Figure 9-3.

Timing Diagram for Complete Successful Bit Check (Number of Checked Bits: 3)

As seen in Figure 9-4, the time window for the bit check is defined by two separate time limits. If

the edge-to-edge time t

ee is in between the lower bit-check limit TLim_min and the upper bit-check

limit T

Lim_max, the check will be continued. If tee is smaller than limit TLim_min or exceeds TLim_max,

the bit check will be terminated and the transceiver switches to sleep mode.

Figure 9-4.

Valid Time Window for Bit Check

Bit check mode

Bit check ok

Start-up mode

Receiving mode

1/2 Bit

RX_ACTIVE

Demod_Out

Bit check

Startup_Sig_Proc

Bit-check

Demod_Out

1/f

Sig

Lim_min

Lim_max

ATA5423-PLSW Datasheet(PDF) 56 Page - ATMEL Corporation

ATA5423-PLSW Datasheet(HTML) 56 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

Datasheet Download

Link URL