RPM-Based PWM Fan Controller
Datasheet
3.2.2
Read Byte
The Read Byte protocol is used to read one byte of data from the registers as shown in Table 3.3.
Table 3.3 Read Byte Protocol
START
SLAVE
ADDRESS
WR
ACK
Register
Address
ACK
START
Slave
Address
RD
ACK
Register
Data
NACK
STOP
1 -> 0
YYYY_YYYb
0
0
XXh
0
0 -> 1
YYYY_YYYb
1
0
XXh
1
0 -> 1
3.2.3
Send Byte
The Send Byte protocol is used to set the internal address register pointer to the correct address
location. No data is transferred during the Send Byte protocol as shown in Table 3.4.
Table 3.4 Send Byte Protocol
SLAVE
ADDRESS
REGISTER
ADDRESS
START
1 -> 0
WR
ACK
ACK
STOP
YYYY_YYYb
0
0
XXh
0
0 -> 1
3.2.4
Receive Byte
The Receive Byte protocol is used to read data from a register when the internal register address
pointer is known to be at the right location (e.g. set via Send Byte). This is used for consecutive reads
of the same register as shown in Table 3.5.
Table 3.5 Receive Byte Protocol
SLAVE
START
ADDRESS
RD
ACK
REGISTER DATA
NACK
STOP
1 -> 0
YYYY_YYYb
1
0
XXh
1
0 -> 1
3.2.5
Block Write Protocol
The Block Write is used to write multiple data bytes to a group of contiguous registers as shown in
Table 3.6. It is an extension of the Write Byte Protocol.
Table 3.6 Block Write Protocol
SLAVE
ADDRESS
REGISTER
ADDRESS
REGISTER
DATA
START
WR
ACK
ACK
ACK
1 ->0
YYYY_YYYb
0
0
XXh
0
XXh
0
REGISTER
DATA
REGISTER
DATA
REGISTER
DATA
ACK
ACK
. . .
ACK
STOP
XXh
0
XXh
0
. . .
XXh
0
0 -> 1
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