LM8333

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SNLS246K – SEPTEMBER 2006 – REVISED MAY 2013

Interrupt Sources

The IRQ output is asserted on these conditions:

•

Any new key-event.

•

Any error condition, which is indicated by the error code.

•

Any enabled interrupt on either of the GEN_IO_0 or GEN_IO_1 pins that can be configured as external

interrupt inputs. When enabled, any rising or falling edge triggers an interrupt.

The IRQ output remains asserted until the interrupt code is read.

Device Operation

EVENT CODE ASSIGNMENT

After power-on reset, the LM8333 starts scanning the keypad. It stays active for a default time of about 500 ms

after the last key is released, after which it enters a standby mode to minimize power consumption (<2 µA

standby current).

Table 1 lists the codes assigned to the matrix positions encoded by the hardware. Key-press events are

assigned the codes listed in Table 1, but with the MSB set. When a key is released, the MSB of the code is

clear.

Table 1. Keypad Matrix Code Assignments

K_OUT0

K_OUT1

K_OUT2

K_OUT3

K_OUT4

K_OUT5

K_OUT6

K_OUT7

SF Keys

WAKE_IN0

0x01

0x02

0x03

0x04

0x05

0x06

0x07

0x08

0x09

WAKE_IN1

0x11

0x12

0x13

0x14

0x15

0x16

0x17

0x18

0x19

WAKE_IN2

0x21

0x22

0x23

0x24

0x25

0x26

0x27

0x28

0x29

WAKE_IN3

0x31

0x32

0x33

0x34

0x35

0x36

0x37

0x38

0x39

WAKE_IN4

0x41

0x42

0x43

0x44

0x45

0x46

0x47

0x48

0x49

WAKE_IN5

0x51

0x52

0x53

0x54

0x55

0x56

0x57

0x58

0x59

WAKE_IN6

0x61

0x62

0x63

0x64

0x65

0x66

0x67

0x68

0x69

WAKE_IN7

0x71

0x72

0x73

0x74

0x75

0x76

0x77

0x78

0x79

The codes are loaded into the FIFO buffer in the order in which they occurred. Table 2 shows an example

sequence of events, and Figure 4 shows the resulting sequence of event codes loaded into the FIFO buffer.

Table 2. Example Sequence of Events

Event Number

Event Code

Event on Input

Matrix Node

Description

1

0xF1

Wake_INP7

K_OUT0

Key is pressed

2

0xB6

Wake_INP3

K_OUT5

Key is pressed

3

0x71

Wake_INP7

K_OUT0

Key is released

4

0x36

Wake_INP3

K_OUT5

Key is released

5

0xB4

Wake_INP3

K_OUT3

Key is pressed

6

0x34

Wake_INP3

K_OUT3

Key is released33

7

0x91

Wake_INP1

K_OUT0

Key is pressed

8

0x00

NA

NA

Indicates end of stored events

Figure 4. Example Event Codes Loaded in FIFO Buffer

I/O EXPANSION

In addition to keypad scanning, the LM8333 supports various I/O expansion options.

Copyright © 2006–2013, Texas Instruments Incorporated

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