MPR084

Sensors

14

Freescale Semiconductor

Preliminary

4

Modes of Operation

4.1

Introduction

The operating modes of the MPR084 are described in this section. Implementation and functionality of each mode are described.

The Modes of Operation of the MPR084 combine to form a suite of quick response and low power consumption functionality. This

is achieved through 2 Run modes and 2 Stop Modes. The two modes are enabled by toggling the Configuration Register’s DCE

and RUNE bits as shown in Table 8. Note that while in a run mode, the only register that can be written to is the Configuration

Register. Thus, when changes to registers are needed, enter Stop1 mode, write to the registers and change the mode to “Run”.

4.2

Initial Power Up

On power-up, the interrupt output IRQ is reset, and IRQ will go high. The registers are reset to the values shown in Table 9.

Table 8. Mode Enable Register Bits

Mode

RUNE

DCE

Run1

1

1

Run2

1

0

Stop1

0

1

Stop2

0

0

Table 9. Power-Up Register Configurations

Register Function

Power-Up Condition

Register Address

HEX Value

FIFO Register

FIFO is empty

0x00

0x40

Fault Register

No faults

0x01

0x00

Touch Pad Status Register

Touch Pad is untouched

0x02

0x00

Touch Pad Configuration Register

Touch Pad is enabled, without interrupts,

with sounder enabled and Auto-Cal Disabled

0x03

0x81

Sensitivity Threshold Registers 1

Maximum sensitivity

0x04

0x00

Sensitivity Threshold Registers 2

Maximum sensitivity

0x05

0x00

Sensitivity Threshold Registers 3

Maximum sensitivity

0x06

0x00

Sensitivity Threshold Registers 4

Maximum sensitivity

0x07

0x00

Sensitivity Threshold Registers 5

Maximum sensitivity

0x08

0x00

Sensitivity Threshold Registers 6

Maximum sensitivity

0x09

0x00

Sensitivity Threshold Registers 7

Maximum sensitivity

0x0A

0x00

Sensitivity Threshold Registers 8

Maximum sensitivity

0x0B

0x00

Electrode Channel Enable Mask

Register

All channels enabled

0x0C

0xFF

Maximum Number of Touched

Positions Register

4 maximum concurrent touched position

allowed

0x0D

0x04

Master Tick Period Register

Master tick period is 10ms

0x0E

0x05

Touch Acquisition Sample Period

Register

TASP is 1 master tick period

0x0F

0x01

Sounder Configuration Register

Sounder is globally enabled, 10ms of 1kHz

0x10

0x01

Low Power Configuration Register

Low Power Mode is disabled

0x11

0x00

Stuck Key Timeout Register

Stuck key detector disabled

0x12

0x00

Configuration Register

Stop1 Mode. IRQ is disabled

0x13

0x14

Sensor Information Register

Fixed SensorInfo based on revision

0x14

0xFF