Datasheet

UCBRSx
7+m [i]
UCBRFx
j=0
m [j]
å
( )
15
bit,RX UCBRSx UCBRFx
BRCLK
j=0
1
T [i] = 16 + m [i] × UCBRx + m [j]
f
æ ö
ç ÷
ç ÷
ç ÷
è ø
å
( )
UCBRSx
7+m [i]
i-1
bit,RX SYNC bit,RX UCBRSx UCBRFx
BRCLK
j=0 j=0
1
t [i] = t + T [j] + 8 + m [i] × UCBRx + m [j]
f
æ ö
ç ÷
ç ÷
ç ÷
è ø
å å
( )
bit,RX UCBRSx
BRCLK
1
T [i] = UCBRx + m [i]
f
i-1
bit,RX SYNC bit,RX UCBRSx
BRCLK
j=0
1 1
t [i] = t + T [j] + INT UCBRx + m [i]
f 2
æ ö
æ ö
ç ÷
ç ÷
ç ÷
è ø
è ø
å
bit,ideal,RX
1
t [i] = (i + 0.5)
Baud rate
1 2 3 4 5 6
0
i
t
0
t
ideal
7 8
1
t
1
2
9 10 11 12 13 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6 7
t
0
t
1
t
2
ST D0 D1
D0 D1
ST
Synchronization Error ± 0.5x BRCLK
Majority Vote Taken Majority Vote Taken Majority Vote Taken
BRCLK
UCAxRXD
RXD synch.
t
actual
Sample
RXD synch.
www.ti.com USCI Operation: UART Mode
Figure 15-11. Receive Error
The ideal sampling time is in the middle of a bit period:
The real sampling time is equal to the sum of all previous bits according to the formulas shown in the
transmit timing section, plus one half BITCLK for the current bit i, plus the synchronization error t
SYNC
.
This results in the following for the low-frequency baud rate mode:
Where,
m
UCBRSx
[i] = Modulation of bit i from Table 15-2
For the oversampling baud rate mode the sampling time of bit i is calculated by:
Where,
= Sum of ones from columns 0 - from the corresponding row in Table 15-3
m
UCBRSx
[i] = Modulation of bit i from Table 15-2
This results in an error normalized to one ideal bit time (1/baudrate) according to the following formula:
Error
RX
[i] = (t
bit,RX
[i] − t
bit,ideal,RX
[i]) × Baudrate × 100%
423
SLAU144J–December 2004–Revised July 2013 Universal Serial Communication Interface, UART Mode
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