SMS48
PreliminaryInformation
2
I C INTERFACE
InputDataProtocol
CONFIGURATION REGISTER OPERATION
The protocol defines any device that sends data onto the
bus as a transmitter and any device that receives data as
a receiver. The device controlling data transmission is
called the Master and the controlled device is called the
Slave. InallcasestheSMS48willbeaSlavedevice,since
it never initiates any data transfers.
Datafortheconfigurationregistersarereadandwrittenvia
an industry standard two-wire interface. The bus was
designed for two-way, two-line serial communication be-
tween different integrated circuits. The two lines are a
serial data line (SDA) and a serial clock line (SCL). The
SDA line must be connected to a positive supply by a pull-
upresistor,locatedsomewhereonthebus. SeeOperating
Characteristics: Table 8 and Figure 7.
One data bit is transferred during each clock pulse. The
data on the SDA line must remain stable during clock high
time because changes on the data line while SCL is high
will be interpreted as start or stop condition.
Symbol
fSCL
Parameter
SCL clock frequency
Clock low period
Conditions
MIN
0
TYP
MAX
Units
kHz
µs
100
tLOW
tHIGH
tBUF
4.7
4.0
4.7
4.7
4.0
4.7
0.2
0.2
Clock high period
µs
Bus free time (1)
Before new transmission
µs
tSU:STA
tHD:STA
tSU:STO
tAA
Start condition setup time
Start condition hold time
Stop condition setup time
Clock edge to valid output
Data Out hold time
µs
µs
µs
SCL low to valid SDA (cycle n)
3.5
µs
tDH
SCL low (cycle n+1) to SDA change
µs
tR
SCL and SDA rise time (1)
SCL and SDA fall time (1)
Data In setup time
1000
300
ns
tF
ns
tSU:DAT
tHD:DAT
TI
250
0
ns
Data In hold time
ns
Noise filter SCL and SDA
Write cycle time
Noise suppression
100
ns
tWR
5
ms
Note (1): These values are guaranteed by design.
Table 8. I2C Operating Characteristics
t
t
LOW
HIGH
t
t
R
F
SCL
t
t
t
t
SU:STO
t
HD:DAT
SU:STA
SU:DAT
HD:STA
t
BUF
SDA In
t
t
AA
DH
SDA Out
Figure 7 - I2C Operating Characteristics
SUMMIT MICROELECTRONICS, Inc.
2088 1.1 04/11/05
11
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
