189
AT90PWM216/316 [DATASHEET]
7710H–AVR–07/2013
The following equations can be used to calculate the ratio of the incoming data rate and internal receiver baud rate.
D
Sum of character size and parity size (D = 5 to 10 bit)
S
Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double Speed
mode.
S
F
First sample number used for majority voting. S
F = 8 for normal speed and SF = 4
for Double Speed mode.
S
M
Middle sample number used for majority voting. S
M = 9 for normal speed and
S
M = 5 for Double Speed mode.
R
slow
is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver
baud
rate.
R
fast is the ratio of the fastest incoming data rate that can be accepted in relation to the
receiver baud rate.
Table 17-2 and
Table 17-3 list the maximum receiver baud rate error that can be tolerated. Note that Normal
Speed mode has higher toleration of baud rate variations.
Table 1.
Table 17-2.
Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode (U2X = 0)
D
# (Data+Parity Bit)
R
slow (%)
R
fast (%)
Max Total Error (%)
Recommended Max
Receiver Error (%)
5
93.20
106.67
+6.67/-6.8
± 3.0
6
94.12
105.79
+5.79/-5.88
± 2.5
7
94.81
105.11
+5.11/-5.19
± 2.0
8
95.36
104.58
+4.58/-4.54
± 2.0
9
95.81
104.14
+4.14/-4.19
± 1.5
10
96.17
103.78
+3.78/-3.83
± 1.5
Table 17-3.
Recommended Maximum Receiver Baud Rate Error for Double Speed Mode (U2X = 1)
D
# (Data+Parity Bit)
Rslow (%)
Rfast (%)
Max Total Error (%)
Recommended Max
Receiver Error (%)
5
94.12
105.66
+5.66/-5.88
± 2.5
6
94.92
104.92
+4.92/-5.08
± 2.0
7
95.52
104,35
+4.35/-4.48
± 1.5
8
96.00
103.90
+3.90/-4.00
± 1.5
9
96.39
103.53
+3.53/-3.61
± 1.5
10
96.70
103.23
+3.23/-3.30
± 1.0
R
slow
D
1
+
S
1
–
DS
S
F
++
-------------------------------------------
=
R
fast
D
2
+
S
D
1
+
SS
M
+
-----------------------------------
=