Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK データシート
製品コード
AT91SAM9M10-G45-EK
509
SAM9M10 [DATASHEET]
6355F–ATARM–12-Mar-13
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%.
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:
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
31.7.8.8
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.
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):
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.
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
error occurs (see
). Only the 6 least significant bits of the IDCHR field are updated with the
received Identifier. The bits 6 and 7 are stuck at 0.
• PARDIS = 1:
F
NOM
min
(
)
100
0.5
8
2
Over
–
(
)
×
×
1
+
[
] Baudrate
×
8
15
–
100
100
----------
1
+
⎝
⎠
⎛
⎞
×
1%
×
------------------------------------------------------------------------------------------------
×
⎝
⎠
⎜
⎟
⎜
⎟
⎜
⎟
⎛
⎞
Hz
=
4
–
α +4 -1 β +1
< <
≤ ≤
F
NOM
(min)
100
4
8
2
Over
–
(
)
×
×
1
+
[
] Baudrate
×
8
15
–
100
100
----------
1
+
⎝
⎠
⎛
⎞
×
1%
×
-------------------------------------------------------------------------------------------
×
⎝
⎠
⎜
⎟
⎜
⎟
⎜
⎟
⎛
⎞
Hz
=