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PCA9502 Datasheet PDF : 25 Pages
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NXP Semiconductors
PCA9502
8-bit I/O expander with I2C-bus/SPI interface
9.3 Addressing
Before any data is transmitted or received, the master must send the address of the
receiver via the SDA line. The first byte after the START condition carries the address of
the slave device and the read/write bit. Table 11 shows how the PCA9502’s address can
be selected by using A1 and A0 pins. For example, if these 2 pins are connected to VDD,
then the PCA9502’s address is set to 0x90, and the master communicates with it through
this address.
Table 11.
A1
VDD
VDD
VDD
VDD
VSS
VSS
VSS
VSS
SCL
SCL
SCL
SCL
SDA
SDA
SDA
SDA
PCA9502 address map
A0
PCA9502 I2C-bus addresses (hex)[1]
VDD
VSS
SCL
0x90 (1001 000X)
0x92 (1001 001X)
0x94 (1001 010X)
SDA
0x96 (1001 011X)
VDD
VSS
SCL
0x98 (1001 100X)
0x9A (1001 101X)
0x9C (1001 110X)
SDA
0x9E (1001 111X)
VDD
VSS
SCL
0xA0 (1010 000X)
0xA2 (1010 001X)
0xA4 (1010 010X)
SDA
0xA6 (1010 011X)
VDD
VSS
SCL
0xA8 (1010 100X)
0xAA (1010 101X)
0xAC (1010 110X)
SDA
0xAE (1010 111X)
[1] X = logic 0 for write cycle; X = logic 1 for read cycle.
9.4 Use of sub-addresses
When a master communicates with the PCA9502 it must send a sub-address in the byte
following the slave address byte. This sub-address is the internal address of the word the
master wants to access for a single byte transfer, or the beginning of a sequence of
locations for a multi-byte transfer. A sub-address is an 8-bit byte. Unlike the device
address, it does not contain a direction (R/W) bit, and like any byte transferred on the bus
it must be followed by an acknowledge.
A register write cycle is shown in Figure 10. The START is followed by a slave address
byte with the direction bit set to ‘write’, a sub-address byte, a number of data bytes, and a
STOP signal. The sub-address indicates which register the master wants to access. and
the data bytes which follow will be written one after the other to the sub-address location.
PCA9502_3
Product data sheet
Rev. 03 — 13 October 2006
© NXP B.V. 2006. All rights reserved.
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