303
7530J–AVR–03/12
Atmel ATmega48/88/168 Automotive
26.8.1
RC Oscillator Precision for LIN Slave implementation
For LIN slave devices, the precision of the RC oscillator before and after re-synchronization are
27. 2-wire Serial Interface Characteristics
Table 27-1 describes the requirements for devices connected to the 2-wire Serial Bus. The ATmega48/88/168 2-wire Serial
Interface meets or exceeds these requirements under the noted conditions.
Table 26-2.
Oscillator Tolerance Before and After re-Synchronization Algorithm
(2.7V<V
CC<5.5V, -40°C to +125°C)
Parameter
Clock Tolerance
ΔF/F
Master
FTOL_UNSYNCH
Deviation of slave node clock from the nominal clock rate before
synchronization; relevant for nodes making use of
synchronization and direct SYNCH BREAK detection.
±14.0 %
F
TOL_SYNCH
Deviation of slave node clock relative to the master node clock
after synchronization; relevant for nodes making use of
synchronization; any slave node must stay within this tolerance
for all fields of a frame which follow the SYNCH FIELD.
Note: For communication between any two nodes their bit rate
must not differ by more than ±2%.
±2.0 %
Table 27-1.
2-wire Serial Bus Requirements
Symbol
Parameter
Condition
Min
Max
Units
VIL
Input Low-voltage
-0.5
0.3 VCC
V
VIH
Input High-voltage
0.7 V
CC
V
CC + 0.5
V
Hysteresis of Schmitt Trigger Inputs
–V
VOL
Output Low-voltage
3 mA sink current
0
0.4
V
Rise Time for both SDA and SCL
20 + 0.1C
300
ns
tof
Output Fall Time from VIHmin to VILmax
250
ns
tSP
Spikes Suppressed by Input Filter
0
ns
I
i
Input Current each I/O Pin
0.1V
CC < Vi < 0.9VCC
-10
10
A
Capacitance for each I/O Pin
–
10
pF
fSCL
SCL Clock Frequency
fCK
SCL, 250kHz)
0
400
kHz
Rp
Value of Pull-up resistor
f
SCL ≤100 kHz
f
SCL > 100 kHz
t
HD;STA
Hold Time (repeated) START Condition
f
SCL ≤100 kHz
4.0
–
s
fSCL > 100 kHz
0.6
–
s
tLOW
Low Period of the SCL Clock
f
SCL ≤100 kHz
4.7
–
s
f
SCL > 100 kHz
1.3
–
s
VCC 0,4V
–
3mA
----------------------------
1000ns
Cb
-------------------
Ω
VCC 0,4V
–
3mA
----------------------------
300ns
Cb
----------------
Ω