ICS9148-47 Datasheet, PDF (3/9 Pages) Integrated Circuit Systems – Pentium/ProTM System Clock Chip

ICS9148-47
General I²C serial interface information
The information in this section assumes familiarity with I²C programming. For more information, contact ICS for an I²C
programming application note.
How to Write:
• Send the address D2_(H) .
• Send two additional dummy bytes, a command code
and byte count.
• Send the desired number of data bytes.
See the diagram below:
Clock Generator
Address (7 bits)
A(6:0) & R/W#
D2(H)
+ 8 bits
ACK
dummy
ACK
command code
+ 8 bits
dummy Byte
count
ACK
Data Byte
1
ACK
Data Byte
N
ACK
Note that the acknowledge bit is sent by the clock chip, and pulls the data line low. There is no minimum of data bytes that must
be sent.
How to Read:
• Send the address D3_(H).
• Send the byte count in binary coded decimal
• Read back the desired number of data bytes
See the diagram below:
Clock Generator
Address (7 bits)
A(6:0) & R/W#
D3(H)
ACK
Byte
Count
ACK
Data Byte
1
ACK
Data Byte
N
The following specifications should be observed:
1. Operating voltage for I²C pins is 3.3V
2. Maximum data transfer rate (SCLK) is 100K bits/sec.
3