Receiving mode – Rainbow Electronics ATA5812 User Manual

Page 55

ATA5811/ATA5812 [Preliminary]

4689B–RKE–04/04

In the presence of a valid transmitter signal, T

Bit-check

is dependent on the frequency of

that signal, f

Sig

, and the count of the bits, N

Bit-check

. A higher value for N

Bit-check

thereby

results in a longer period for T

Bit-check

requiring a higher value for the transmitter pre-

burst T

Preburst

Receiving Mode

If the Bit-check was successful for all bits specified by N

Bit-check

, the transceiver switches

to receiving mode. To activate a connected microcontroller, the bits VSOUT_EN and
CLK_ON in control register 3 are set to 1. An interrupt is issued at pin IRQ if the control
bits T_MODE = 0 and P_MODE = 0.

If the transparent mode is active (T_MODE = 1) and the level on pin CS is low (no data
transfer via the serial interface), the RX data stream is available on pin SDO_TMDO
(Figure 47).

Figure 47. Receiving Mode (TMODE = 1)

If the transparent mode is inactive (T_MODE = 0), the received data stream is buffered
in the TX/RX data buffer (see Figure 48 on page 56). The TX/RX data buffer is only
usable for Manchester and Bi-phase coded signals. It is permanently possible to trans-
fer the data from the data buffer via the 4-wire serial interface to a microcontroller (see
Figure 33 on page 45).

Buffering of the data stream:

After a successful Bit-check, the transceiver switches from Bit-check mode to receiving
mode. In receiving mode the TX/RX data buffer control logic is active and examines the
incoming data stream. This is done, like in the Bit-check, by subsequent time frame
checks where the distance between two edges is continuously compared to a program-
mable time window as illustrated in Figure 48 on page 56, only two distances between
two edges in Manchester and Bi-phase coded signals are valid (T and 2T).

The limits for T are the same as used for the Bit-check. They can be programmed in
control register 5 and 6 (Lim_min, Lim_max).

The limits for 2T are calculated as follows:

Lower limit of 2T:

Upper limit of 2T:

If the result of Lim_min_2T or Lim_max_2T is not an integer value, it will be round up.

Demod_Out

Preburst

Start-

bit

'0'

'0' '0'

'0'

'1'

'0'

'0' '0'

'0'

'1'

'1' '1'

'1' '0'

Byte 1

Byte 2

Byte 3

'0'

'1'

'0' '1'

'1'

'0' '0'

Bit check ok

SDO_TMDO

Bit-check mode

Receiving mode

Lim_min_2T

Lim_min

Lim_max

(

)

Lim_max

Lim_min

–

(

)

⁄

–

Lim_min_2T

XDCLK

Lim_max_2T

Lim_min

Lim_max

(

)

Lim_max

Lim_min

–

(

)

⁄

Lim_max_2T

Lim_max_2T - 1

(

)

XDCLK