Datasheet
MCP4017/18/19
DS22147A-page 38 © 2009 Microchip Technology Inc.
5.4.1 WRITE OPERATION
The write operation requires the START condition,
Control Byte, Acknowledge, Data Byte, Acknowledge
and STOP (or RESTART) condition. The Control (Slave
Address) Byte requires the R/W
bit equal to a logic zero
(R/W
= “0”) to generate a write sequence. The
MCP4017/18/19 is responsible for generating the
Acknowledge (A) bits.
Data is written to the MCP4017/18/19 after every byte
transfer (during the A bit). If a STOP or RESTART
condition is generated during a data transfer (before
the A bit), the data will not be written to MCP4017/18/
19.
Data bytes may be written after each Acknowledge.
The command is terminated once a Stop (P) condition
occurs. Refer to Figure 5-12 for the write sequence.
For a single byte write, the master sends a STOP or
RESTART condition after the 1st data byte is sent.
The MSb of each Data Byte is a don’t care, since the
wiper register is only 7-bits wide.
Figure 5-14 shows the I
2
C communication behavior of
the Master Device and the MCP4017/18/19 device and
the resultant I
2
C bus values.
5.4.2 READ OPERATIONS
The read operation requires the START condition,
Control Byte, Acknowledge, Data Byte, the master
generating the A
and STOP condition. The Control
Byte requires the R/W bit equal to a logic one (R/W =
1) to generate a read sequence. The MCP4017/18/19
will A the Slave Address Byte and A
all the Data Bytes.
The I
2
C Master will A the Slave Address Byte and the
last Data Byte. If there are multiple Data Bytes, the I
2
C
Master will A all Data Bytes except the last Data Byte
(which it will A
).
The MCP4017/18/19 maintains control of the SDA
signal until all data bits have been clocked out.
The command is terminated once a Stop (P) condition
occurs. Refer to Figure 5-13 for the read command
sequence. For a single read, the master sends a STOP
or RESTART condition after the 1st data byte (and A
bit) is sent from the slave.
Figure 5-14 shows the I
2
C communication behavior of
the Master Device and the MCP4017/18/19 device and
the resultant I
2
C bus values.
FIGURE 5-12: I
2
C Write Command Format.
STOP bit
Slave Address Byte
Data Byte Data Byte
1010S1110 D3AD2D1D0AD3xD6D5D4 D2D1D0A
Fixed
Address
Data Byte Data Byte
AD3x D6D5D4 D2D1D0 A
P
Read/Write bit (“0” = Write)
xD6D5D4
D3 D2 D1 D0
xD6D5D4
S = Start Condition
P = Stop Condition
A = Acknowledge
X = Don’t Care
R/W = Read/Write bit
D6, D5, D4, D3, D2, D1, D0 = Data bits
Legend