ATA6613 ATMEL Corporation, ATA6613 Datasheet - Page 209

• Manufacturer Part Number: ATA6613
• Description: Ata6613
• Manufacturer: ATMEL Corporation

Figure 6-74. Sampling of Data and Parity Bit
Figure 6-75. Stop Bit Sampling and Next Start Bit Sampling
9111C–AUTO–02/08
(U2X = 0)
(U2X = 1)
(U2X = 0)
(U2X = 1)
Sample
Sample
Sample
Sample
RxD
RxD
The decision of the logic level of the received bit is taken by doing a majority voting of the logic
value to the three samples in the center of the received bit. The center samples are emphasized
on the figure by having the sample number inside boxes. The majority voting process is done as
follows: If two or all three samples have high levels, the received bit is registered to be a logic 1.
If two or all three samples have low levels, the received bit is registered to be a logic 0. This
majority voting process acts as a low pass filter for the incoming signal on the RxDn pin. The
recovery process is then repeated until a complete frame is received. Including the first stop bit.
Note that the Receiver only uses the first stop bit of a frame.
Figure 6-75
of the next frame.
The same majority voting is done to the stop bit as done for the other bits in the frame. If the stop
bit is registered to have a logic 0 value, the Frame Error (FEn) Flag will be set.
A new high to low transition indicating the start bit of a new frame can come right after the last of
the bits used for majority voting. For Normal Speed mode, the first low level sample can be at
point marked (A) in
(B). (C) marks a stop bit of full length. The early start bit detection influences the operational
range of the Receiver.
1
1
1
1
2
2
shows the sampling of the stop bit and the earliest possible beginning of the start bit
3
2
3
2
4
4
Figure
5
3
5
3
6
6
6-75. For Double Speed mode the first low level must be delayed to
7
4
7
4
8
8
STOP 1
BIT n
9
5
9
5
10
10
(A)
0/1 0/1 0/1
11
6
6
12
(B)
0/1
13
7
ATA6612/ATA6613
14
15
8
16
(C)
1
1
209