saa-xc866 Infineon Technologies Corporation, saa-xc866 Datasheet - Page 72

• Manufacturer Part Number: saa-xc866
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Infineon Technologies Corporation

• 8-bit reload value (BR_VALUE) for the baud rate timer defined by register BG
The following formulas calculate the final baud rate without and with the fractional divider
respectively:
The maximum baud rate that can be generated is limited to
clock of 26.7 MHz, the maximum achievable baud rate is 0.83 MBaud.
Standard LIN protocal can support a maximum baud rate of 20kHz, the baud rate
accuracy is not critical and the fractional divider can be disabled. Only the prescaler is
used for auto baud rate calculation. For LIN fast mode, which supports the baud rate of
20kHz to 115.2kHz, the higher baud rates require the use of the fractional divider for
greater accuracy.
Table 26
settings and deviation errors. The fractional divider is disabled and a module clock of
26.7 MHz is used.
Table 26
Baud rate
19.2 kBaud
9600 Baud
4800 Baud
2400 Baud
The fractional divider allows baud rates of higher accuracy (lower deviation error) to be
generated.
115.2 kHz, using different module clock frequencies. The fractional divider is enabled
(fractional divider mode) and the corresponding parameter settings are shown.
Data Sheet
baud rate
lists the various commonly used baud rates with their corresponding parameter
=
Table 27
---------------------------------------------------------------------------------- - where 2
16 2
Typical Baud rates for UART with Fractional Divider disabled
×
baud rate
BRPRE
lists the resulting deviation errors from generating a baud rate of
Prescaling Factor
(2
1 (BRPRE=000
1 (BRPRE=000
2 (BRPRE=001
4 (BRPRE=010
BRPRE
×
f
=
PCLK
(
BR_VALUE
---------------------------------------------------------------------------------- -
16 2
)
×
BRPRE
B
B
B
B
)
)
)
)
+
×
f
68
PCLK
1
(
)
BR_VALUE
Reload Value
(BR_VALUE + 1)
174 (AE
174 (AE
174 (AE
87 (57
H
H
H
H
)
BRPRE
)
)
)
+
f
PCLK
1
)
×
×
Functional Description
/32. Hence, for a module
STEP
-------------- -
(
256
BR_VALUE
Deviation Error
-0.22 %
-0.22 %
-0.22 %
-0.22 %
SAA-XC866
V1.2, 2008-02
+
1
) 1
>