577
11028E–ATARM–22-Apr-13
SAM9G46
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
33.7.8.8
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.
Baudrate_deviation
100
α
[
8
2
Over
–
() β
+
] Baudrate
×
8F
SLAVE
×
--------------------------------------------------------------------------------------------
×
%
=
Baudrate_deviation
100
α
[
8
2
Over
–
() 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
=