Cp3bt26 – National CP3BT26 User Manual
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164
CP3BT26
Data bits are sensed by taking a majority vote of three sam-
ples latched near the midpoint of each baud (bit time). Nor-
mally, the position of the samples within the baud is
determined automatically, but software can override the au-
tomatic selection by setting the USMD bit in the UnMDSL2
register and programming the UnSPOS register.
Serial data input on the RXD pin is shifted into the RSFT
register. On receiving the complete character, the contents
of the RSFT register are copied into the UnRBUF register
and the Receive Buffer Full bit (URBF) is set. The URBF bit
is automatically cleared when software reads the character
from the URBUF register. The RSFT register is not software
accessible.
Figure 76.
UART Block Diagram
Figure 77.
UART Asynchronous Communication
TXD
Transmitter
Control and
Error Detection
Parity
Generator/Checker
RXD
Receiver
CKX
Baud Rate
Generator
Baud Clock
Baud Clock
System Clock
Inter
nal Bus
DS060
RTS
CTS
Flow Control
Logic
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
Sample
Sample
Sample
DATA (LSB)
STARTBIT
DATABIT
DS061