Atmel Xplained Pro Evaluation Kit ATSAMD20-XPRO ATSAMD20-XPRO Data Sheet
Product codes
ATSAMD20-XPRO
333
Atmel | SMART SAM D20 [DATASHEET]
Atmel-42129K–SAM-D20_datasheet–06/2014
Figure 23-3. Baud Rate Generator
contains equations for calculating the baud rate (in bits per second) and for calculating the BAUD register
value for each mode of operation.
For asynchronous mode, the BAUD register value is 16 bits (0 to 65,535), while for synchronous mode, the BAUD
register value is 8 bits (0 to 255).
register value is 8 bits (0 to 255).
Table 23-2. Baud Rate Equations
Asynchronous Mode BAUD Value Selection
The formula given for f
BAUD
calculates the average frequency over 65,536 f
REF
cycles. Although the BAUD register can be
set to any value between 0 and 65,536, the values that will change the average frequency of f
BAUD
over a single frame
are more constrained. The BAUD register values that will affect the average frequency over a single frame lead to an
integer increase in the cycles per frame (CPF)
integer increase in the cycles per frame (CPF)
where
z
D represent the data bits per frame
z
S represent the sum of start and first stop bits, if present
Base
Period
Selectable
Internal Clk
(GCLK)
Ext Clk
CTRLA.MODE[0]
0
1
0
1
0
1
0
1
f
ref
Clock
Recovery
Tx Clk
Rx Clk
CTRLA.MODE
/2
/8
/1
/2
/16
Baud Rate Generator
Operating Mode
Condition
Baud Rate (Bits Per Second)
BAUD Register Value Calculation
Asynchronous
Synchronous
16
f
f
REF
BAUD
≤
⎟
⎠
⎞
⎜
⎝
⎛
−
=
536
,
65
1
16
BAUD
f
f
REF
BAUD
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
=
f
f
REF
BAUD
BAUD
16
1
536
,
65
2
f
f
REF
BAUD
≤
)
1
(
2
+
=
BAUD
f
f
REF
BAUD
1
2
−
=
f
f
BAUD
REF
BAUD
)
(
S
D
CPF
f
f
BAUD
REF
+
=