17

Notes on Power-up

The ADNS-7550 does not perform an internal power up

self-reset; the POWER_UP_RESET register must be written

every time power is applied. The appropriate sequence is

as follows:

i.

Apply power to VDD5 and VDDIO in any order, with

the delay of no more than 100ms in between each

supply. Ensure all supplies are stable.

ii.

Drive NCS high, then low to reset the SPI port.

iii.

Write 0x5a to register 0x3a.

iv.

Wait for at least one frame.

v.

Clear observation register.

vi.

Wait at least one frame and check observation

register, all bits 0-3 must be set.

vii. Read from registers 0x02, 0x03, 0x04 and 0x05 (or

read these same 4 bytes from burst motion register

0x42) one time regardless of the motion pin state.

viii. Write 0x27 to register 0x3C

ix.

Write 0x0a to register 0x22

x.

Write 0x01 to register 0x21

xi.

Write 0x32 to register 0x3C

xii. Write 0x20 to register 0x23

xiii. Write 0x05 to register 0x3C

xiv. Write 0xB9 to register 0x37

During power-up there will be a period of time after the

power supply is high but before any clocks are available.

The table below shows the state of the various pins

during power-up and reset.

State of Signal Pins After VDD is Valid

Pin

On

Power-Up

Before Reset

After Reset

NCS High

NCS Low

NCS

Functional

Hi

Low

Functional

MISO

Undefined Undefined

Functional

Depends on

NCS

SCLK

Ignored

Ignored

Functional

Depends on

NCS

MOSI

Ignored

Ignored

Functional

Depends on

NCS

MOTION

Undefined Undefined

Undefined Functional

LASER_

NEN

Undefined Undefined

Undefined Functional

Notes on Shutdown

The ADNS-7550 can be set in Shutdown mode by

writing 0xe7 to register 0x3b. The SPI port should not

be accessed when Shutdown mode is asserted, except

the power-up command (writing 0x5a to register 0x3a).

(Other ICs on the same SPI bus can be accessed, as long

as the sensor’s NCS pin is not asserted.) The table below

shows the state of various pins during shutdown. To

deassert Shutdown mode:

i.

Write 0x5a to register 0x3a

ii.

Wait for at least one frame.

iii. Clear observation register.

iv. Wait at least one frame

v.

Check observation register, all bits 0-3 must be set to

1.

vi. Write 0x27 to register 0x3C

vii. Write 0x0a to register 0x22

viii. Write 0x01 to register 0x21

ix. Write 0x32 to register 0x3C

x.

Write 0x20 to register 0x23

xi. Write 0x05 to register 0x3C

xii. Write 0xB9 to register 0x37

xiii. Any register settings must then be reloaded.

Pin

Status when Shutdown Mode

NCS

MISO

SCLK

MOSI

LASER_NEN

High(off )

MOTION

1. NCS pin must be held to 1 (high) if SPI bus is shared with other

devices. It is recommended to hold to 1 (high) during Power

Down unless powering up the Sensor. It must be held to 0 (low) if

the sensor is to be re-powered up from shutdown (writing 0x5a to

register 0x3a).

2. Depend on last state

3. SCLK is ignore if NCS is 1 (high). It is functional if NCS is 0 (low).

4. MOSI is ignore if NCS is 1 (high). If NCS is 0 (low), any command

present on the MOSI pin will be ignored except power-up command

(writing 0x5a to register 0x3a).

Note:

There are long wakeup times from shutdown. These features should

not be used for power management during normal mouse motion.

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PixArt Imaging Inc.

PixArt Imaging Inc.

ADNS-7550 Integrated Molded Lead-Frame DIP Sensor