Figure 28. Output of Digital Noise at the End of the Data Stream
BBiittcchheecckkookk
BBiitt cchheecckk ookk
PPrreebbuurrsstt
DDaattaa
DDiiggiittaall NNooiissee
DDiiggiittaallNNooiissee PPrreebbuurrsstt
DDaattaa
DDigigititaallNNooisisee
DDaattaa__oouutt ((DDAATTAA))
DDAATTAA__CCLLKK
Receiving mode,
Receiving mode,
Receiving mode,
Receiving mode,
BBiitt--cchheecckk
mmooddee
RReecceeiivviinnggmmooddee,,
RReecceeivivininggmmooddee,,
bbititcchheecckkaakkttiivvee
data clock control
data clock control
data clock control
data clock control
bbiittcchheecckkaakkttiivvee
logic active
logic active
logic active
logic active
Figure 29. Automatic Noise Suppression
Bit check ok
Bit check ok
Preburst
Preburst
Data
Data
Data_out (DATA)
DATA_CLK
Receiving mode,
data clock control
logic active
Receiving mode,
data clock control
logic active
Bit-check
mode
Bit-check
mode
Bit-check
mode
Figure 30. Occurence of a Pulse at the End of the Data Stream
_
_
OR tee
ee < TLim_min_2T
Lim_max < t
Lim_min OR T
Timing error
(tee < T
Tee
Data stream
Digital noise
'1'
'1'
'1'
Dem_out
Data_out (DATA)
DATA_CLK
T
Pulse
Receiving mode,
data clock control
logic active
Bit-check mode
Controlled Noise Suppression If the bit Noise_Disable (see Table 10) in the OPMODE register is set to 0, digital noise
by the Microcontroller (see
Figure 31)
appears at the end of a valid data stream. To suppress the noise, the Pin POLL-
ING/_ON must be set to Low. The receiver remains in receiving mode. Then, the OFF-
command causes the change to the start-up mode. The programmed sleep time (see
Table 8) will not be executed because the level at Pin POLLING/_ON is low, but the bit
check is active in that case. The OFF-command activates the bit check also if the Pin
POLLING/_ON is held to Low. The receiver changes back to receiving mode if the bit
check was successful. To activate the polling mode at the end of the data transmission,
the Pin POLLING/_ON must be set to High.
This way to suppress the noise is recommended if the data stream is not Manchester or
Bi-phase coded.
22
T5743
4569A–RKE–12/02
ATMEL [ ATMEL ]
