Power One SFP450 Series, Руководство по программированию

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Title
Issued 2006-05-19 SKl
Modified -- --
Mech. Eng. approved -- --
Marketing approved
SFP450/600 I
2
C Interface Programming
Manual
Mfg. approved --
Size Scale Sheet Drawing No. Revision
www.power-one.com
A4 6/21
BBA20005-G 001
Supersedes: -
Example: On the backplane PS A0 is connected to 0V, you will have the following device address to read
a byte from the SFP450/600 EEPROM:
MSB LSB
Bit 7 6 5 4 3 2 1 0
SFP450/600
EEPROM
Device Address 1 0 1 0 1 1 0 1
fix fix fix fix fix fix A0 R
->1010’1101
Bin
=AD
Hex
=173
Dec
4.6 I
2
C Bus Master and clock (SCL) speed
The I
2
C Bus Master controls communications between the Master and all I
2
C devices connected to the
bus. If during an I
2
C communication cycle the SFP450/600 Status Port is interrupted by an internal
service interrupt, the SFP450/600 will hold the SCL line low to force the master into a wait state. Data
transfer will continue when the SFP450/600 releases the SCL line. Please note if the I
2
C bus is
communicating with a clock frequency slower than 6.5kHz, the SCL line will not be held low. The
SFP450/600 EERPOM is an ATMEL AT24C02 compatible device and is not holding down the SCL line.
4.7 Maximum and minimum values for Pull-Up resisters
For I
2
C-bus systems, the values of the Pull-Up resistors depend on the following parameters:
•
Supply voltage
•
Bus capacitance
•
Number of connected devices (input c leakage current).
The supply voltage limits the minimum value of the Pull-Up resistor due to the specified minimum sink
current of 3mA. On a 3.3V supply, this makes
R
min
=3.3V/3mA=1.1k
Ω
.
The bus capacitance is the total capacitance of wire, connections and pins. This capacitance limits the
maximum value of the Pull-Up resister due to the specified rise time. For a System with 380pF
capacitance (two SFP450/600 and a wire capacitance of 100pf)
R
max
=2.1k
Ω
.
For further information concerning the Pull-Up resister, refer to:
I²C Bus specification, 16.1 Maximum and minimum values of resistors Rp and Rs for Standard-mode I2C-bus devices .