pca8574 NXP Semiconductors, pca8574 Datasheet - Page 6

• Manufacturer Part Number: pca8574
• Description: Pca8574/pca8574a Remote 8-bit I/o Expander For I2c-bus With Interrupt
• Manufacturer: NXP Semiconductors

NXP Semiconductors
7. Functional description
PCA8574_PCA8574A_2
Product data sheet
7.1.1 Address maps
7.1 Device address
Refer to
Following a START condition, the bus master must send the address of the slave it is
accessing and the operation it wants to perform (read or write). The address of the
PCA8574/74A is shown in
8 slave addresses. To conserve power, no internal pull-up resistors are incorporated on
AD2, AD1, and AD0. Address values depending on AD2, AD1, and AD0 can be found in
Table 4 “PCA8574 address map”
Remark: When using the PCA8574A, the General Call address (0000 0000b) and the
Device ID address (1111 100Xb) are reserved and cannot be used as device address.
Failure to follow this requirement will cause the PCA8574A not to acknowledge.
The last bit of the first byte defines the operation to be performed. When set to logic 1 a
read is selected, while a logic 0 selects a write operation.
When AD2, AD1 and AD0 are held to V
PCF8574A is applied.
Table 4.
A6
0
0
0
0
0
0
0
0
Fig 7. PCA8574/74A address
Figure 1 “Block diagram of
A5
1
1
1
1
1
1
1
1
PCA8574 address map
A4
0
0
0
0
0
0
0
0
Rev. 02 — 14 May 2007
A3
0
0
0
0
0
0
0
0
Figure
A6
and
7. Slave address pins AD2, AD1, and AD0 choose 1 of
A5
Remote 8-bit I/O expander for I
A2
0
0
0
0
1
1
1
1
PCA8574/74A”.
programmable
Table 5 “PCA8574A address
slave address
A4
DD
A3
A1
0
0
1
1
0
0
1
1
or V
A2
SS
, the same address as the PCF8574 or
A1
A0
0
1
0
1
0
1
0
1
A0
002aab636
R/W
Address
20h
21h
22h
23h
24h
25h
26h
27h
PCA8574/74A
map”.
2
C-bus with interrupt
© NXP B.V. 2007. All rights reserved.
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