Texas Instruments MSP430x4xx Family, User Manual

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USCI Operation: UART Mode
19-21 Universal Serial Communication Interface, UART Mode
For the oversampling baud rate mode the sampling time t
bit,RX
[i] of bit i is
calculated by:
t
bit,RX
[i]
+
t
SYNC
)
ȍ
i
*
1
j
+
0
T
bit,RX
[j]
)
1
f
BRCLK
ǒ
ǒ
8
)
m
UCBRSx
[
i
]
Ǔ @
UCBRx
)
ȍ
7
)
m
UCBRSx
[i]
j
+
0
m
UCBRFx
[j]
Ǔ
where:
T
bit,RX
[i]
+
1
f
BRCLK
ǒ
ǒ
16
)
m
UCBRSx
[i]
Ǔ @
UCBRx
)
ȍ
15
j
+
0
m
UCBRFx
[j]
Ǔ
ȍ
7
)
m
UCBRSx
[i]
j
+
0
m
UCBRFx
[j]: Sum of ones from columns 0 − 7
)
m
UCBRSx
[i]
from the corresponding row in Table 19−3
m
UCBRSx
[i]: Modulation of bit i from Table 19−2
This results in an error normalized to one ideal bit time (1/baudrate) according
to the following formula:
Error
RX
[i]
+
ǒ
t
bit,RX
[i]
*
t
bit,ideal,RX
[i]
Ǔ
@
Baudrate
@
100%
19.3.13 Typical Baud Rates and Errors
Standard baud rate data for UCBRx, UCBRSx and UCBRFx are listed in
Table 19−4 and Table 19−5 for a 32,768 Hz crystal sourcing ACLK and typical
SMCLK frequencies. Please ensure that the selected BRCLK frequency does
not exceed the device specific maximum USCI input frequency. Please refer
to the device-specific data sheet.
The receive error is the accumulated time versus the ideal scanning time in the
middle of each bit. The worst case error is given for the reception of an 8-bit
character with parity and one stop bit including synchronization error.
The transmit error is the accumulated timing error versus the ideal time of the
bit period. The worst case error is given for the transmission of an 8-bit
character with parity and stop bit.