Datasheet

PCA9539A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 2 — 12 August 2013 6 of 39
NXP Semiconductors
PCA9539A
Low voltage 16-bit I
2
C-bus I/O port with interrupt and reset
6.2 Registers
6.2.1 Pointer register and command byte
Following the successful acknowledgement of the address byte, the bus master sends a
command byte, which is stored in the Pointer register in the PCA9539A. The lower
four bits of this data byte state the operation (read or write) and the internal registers
(Input, Output, Polarity Inversion, or Configuration) that will be affected. This register is
write only.
[1] Undefined.
6.2.2 Input port register pair (00h, 01h)
The Input port registers (registers 0 and 1) reflect the incoming logic levels of the pins,
regardless of whether the pin is defined as an input or an output by the Configuration
register. The Input port registers are read only; writes to these registers have no effect.
The default value ‘X’ is determined by the externally applied logic level. An Input port
register read operation is performed as described in Section 7.2 “
Reading the port
registers”.
Fig 5. Pointer register bits
002aaf540
B7 B6 B5 B4 B3 B2 B1 B0
Table 4. Command byte
Pointer register bits Command byte
(hexadecimal)
Register Protocol Power-up
default
B7 B6 B5 B4 B3 B2 B1 B0
0 0 0 0 0 0 0 0 00h Input port 0 read byte xxxx xxxx
[1]
0 0 0 0 0 0 0 1 01h Input port 1 read byte xxxx xxxx
0 0 0 0 0 0 1 0 02h Output port 0 read/write byte 1111 1111
0 0 0 0 0 0 1 1 03h Output port 1 read/write byte 1111 1111
0 0 0 0 0 1 0 0 04h Polarity Inversion port 0 read/write byte 0000 0000
0 0 0 0 0 1 0 1 05h Polarity Inversion port 1 read/write byte 0000 0000
0 0 0 0 0 1 1 0 06h Configuration port 0 read/write byte 1111 1111
0 0 0 0 0 1 1 1 07h Configuration port 1 read/write byte 1111 1111
Table 5. Input port 0 register (address 00h)
Bit 7 6 5 4 3 2 1 0
Symbol I0.7 I0.6 I0.5 I0.4 I0.3 I0.2 I0.1 I0.0
Default XXXXXXXX
Table 6. Input port 1 register (address 01h)
Bit 7 6 5 4 3 2 1 0
Symbol I1.7 I1.6 I1.5 I1.4 I1.3 I1.2 I1.1 I1.0
Default XXXXXXXX