Datasheet
607
32117D–AVR-01/12
AT32UC3C
F
TOL_UNSYNCH
is the deviation of the real slave node clock from the nominal clock frequency. The
LIN Standard imposes that it must not exceed ±15%. The LIN Standard imposes also that for
communication between two nodes, their bit rate must not differ by more than ±2%. This means
that the Baudrate_deviation must not exceed ±1%.
It follows from that, a minimum value for the nominal clock frequency:
Examples:
• Baudrate = 20 kbit/s, Over=0 (Oversampling 16X) => F
Nom
(min) = 2.64 MHz
• Baudrate = 20 kbit/s, Over=1 (Oversampling 8X) => F
Nom
(min) = 1.47 MHz
• Baudrate = 1 kbit/s, Over=0 (Oversampling 16X) => F
Nom
(min) = 132 kHz
• Baudrate = 1 kbit/s, Over=1 (Oversampling 8X) => F
Nom
(min) = 74 kHz
If the fractional baud rate is not used, the accuracy of the synchronization becomes much lower.
When the counter is stopped, the 16 most significant bits of the counter (value divided by 8)
gives the new clock divider (CD). This value is rounded by adding the first insignificant bit. The
equation of the Baudrate deviation is the same as given above, but the constants are as follows:
It follows from that, a minimum value for the nominal clock frequency:
Examples:
• Baudrate = 20 kbit/s, Over=0 (Oversampling 16X) => F
Nom
(min) = 19.12 MHz
• Baudrate = 20 kbit/s, Over=1 (Oversampling 8X) => F
Nom
(min) = 9.71 MHz
• Baudrate = 1 kbit/s, Over=0 (Oversampling 16X) => F
Nom
(min) = 956 kHz
• Baudrate = 1 kbit/s, Over=1 (Oversampling 8X) => F
Nom
(min) = 485 kHz
25.6.9.9 Identifier Parity
A protected identifier consists of two sub-fields; the identifier and the identifier parity. Bits 0 to 5
are assigned to the identifier and bits 6 and 7 are assigned to the parity.
The USART interface can generate/check these parity bits, but this feature can also be disabled.
The user can choose between two modes by the PARDIS bit of the LIN Mode register (LINMR):
Baudrate_deviation 100
α[ 82Over–()β+ ] Baudrate×××
8
F
TOL_UNSYNCH
100
---------------------------------------
⎝⎠
⎛⎞
xF
Nom
×
-------------------------------------------------------------------------------------------- -
×
⎝⎠
⎜⎟
⎜⎟
⎜⎟
⎛⎞
%=
0.5– α +0.5 -1 β +1<<≤≤
F
NOM
min() 100
0.5 8 2 Over–()×× 1+[]Baudrate×
8
15–
100
--------- - 1+
⎝⎠
⎛⎞
× 1%×
------------------------------------------------------------------------------------------------
×
⎝⎠
⎜⎟
⎜⎟
⎜⎟
⎛⎞
Hz=
4– α +4 -1 β +1<<≤≤
F
NOM
(min) 100
4 8 2 Over–()×× 1+[]Baudrate×
8
15–
100
--------- - 1+
⎝⎠
⎛⎞
× 1%×
-------------------------------------------------------------------------------------------
×
⎝⎠
⎜⎟
⎜⎟
⎜⎟
⎛⎞
Hz=