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308
2545T–AVR–05/11
ATmega48/88/168
29.6
2-wire serial interface characteristics
Table 29-5 describes the requirements for devices connected to the 2-wire Serial Bus. The Atmel ATmega48/88/168 2-wire
Serial Interface meets or exceeds these requirements under the noted conditions.
Notes:
1. In ATmega48/88/168, this parameter is characterized and not 100% tested.
2. Required only for f
SCL > 100kHz.
Table 29-5.
2-wire serial bus requirements.
Symbol
Parameter
Condition
Min.
Max.
Units
VIL
Input low-voltage
-0.5
0.3VCC
V
IH
Input high-voltage
0.7V
CC
V
CC + 0.5
Hysteresis of schmitt trigger inputs
–
Output low-voltage
3mA sink current
0
0.4
tr
Rise time for both SDA and SCL
20 + 0.1C
b
300
ns
Output fall time from VIHmin to VILmax
20 + 0.1Cb
250
Spikes suppressed by input filter
0
I
i
Input current each I/O pin
0.1V
CC < Vi < 0.9VCC
-10
10
A
Ci
Capacitance for each I/O pin
–
10
pF
fSCL
SCL clock frequency
fCK
0
400
kHz
Rp
Value of pull-up resistor
f
SCL ≤ 100kHz
f
SCL > 100kHz
t
HD;STA
Hold time (repeated) START condition
f
SCL ≤ 100kHz
4.0
–
s
fSCL > 100kHz
0.6
–
tLOW
Low period of the SCL clock
f
SCL ≤ 100kHz
4.7
–
f
SCL > 100kHz
1.3
–
t
HIGH
High period of the SCL clock
fSCL ≤ 100kHz
4.0
–
f
SCL > 100kHz
0.6
–
t
SU;STA
Setup time for a repeated START condition
f
SCL ≤ 100kHz
4.7
–
fSCL > 100kHz
0.6
–
tHD;DAT
Data hold time
f
SCL ≤ 100kHz
0
3.45
f
SCL > 100kHz
0
0.9
t
SU;DAT
Data setup time
fSCL ≤ 100kHz
250
–
ns
f
SCL > 100kHz
100
–
t
SU;STO
Setup time for STOP condition
f
SCL ≤ 100kHz
4.0
–
s
fSCL > 100kHz
0.6
–
tBUF
Bus free time between a STOP and START
condition
f
SCL ≤ 100kHz
4.7
–
fSCL > 100kHz
1.3
–
VCC 0.4V
–
3mA
----------------------------
1000ns
Cb
-----------------
Ω
VCC 0.4V
–
3mA
----------------------------
300ns
Cb
--------------