Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
810
The following formula is used to compute the deviation of the slave bit rate relative to the master bit rate after
synchronization (F
SLAVE
is the real slave node clock frequency).
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
35.7.8.9 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 (US_LINMR):
 PARDIS = 0:
During header transmission, the parity bits are computed and sent with the 6 least significant bits of the IDCHR
field of the LIN Identifier register (US_LINIR). The bits 6 and 7 of this register are discarded.
During header reception, the parity bits of the identifier are checked. If the parity bits are wrong, an Identifier Parity
error occurs (see Section 35.7.3.8). Only the 6 least significant bits of the IDCHR field are updated with the
received Identifier. The bits 6 and 7 are stuck to 0.
 PARDIS = 1:
During header transmission, all the bits of the IDCHR field of the LIN Identifier register (US_LINIR) are sent on the
bus.
During header reception, all the bits of the IDCHR field are updated with the received Identifier.
Baudrate_deviation 100
α[ 82Over–()β+ ] Baudrate×××
8F
SLAVE
×
----------------------------------------------------------------------------------------
×


%=
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=