ADNS3040 datasheet(14/26 Pages) HP

14 / 26 page

Notes on Shutdown and Forced Rest

The ADNS-3040 can be set in

Rest mode through the

Configuration_Bits register

(0x11). This is to allow for

further power savings in

applications where the sensor

does not need to operate all

the time.

The ADNS-3040 can be set in

Shutdown mode by asserting

the SHTDWN pin. For proper

operation, SHTDWN pulse

width must be at least t

STDWN.

Shorter pulse widths may

cause the chip to enter an

undefined state. In addition,

the SPI port should not be

accessed when SHTDWN is

asserted. (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.

After deasserting SHTDWN, a

full reset must be initiated.

Wait t

WAKEUP before accessing

the SPI port, then write 0x5A

to the POWER_UP_RESET

must then be reloaded.

* NCS pin must be held to 1 (high) if SPI bus is

shared with other devices. It can be in either

state if the sensor is the only device in addition

to the microcontroller.

Note:

There are long wakeup times from shutdown

and forced Rest. These features should not be

used for power management during normal

mouse motion.

Notes on Power-up

The ADNS-3040 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:

1. Apply power

2. Drive NCS high, then low to

reset the SPI port

3. Write 0x5a to register 0x3a

4. Read from registers 0x02,

0x03 and 0x04 (or read

these same 3 bytes from

burst motion

regardless the state of the

motion pin.

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.

On Power-Up

NCS high

before reset

NCS Low

before reset

After Reset

NCS

functional

high

low

functional

MISO

undefined

functional

depends on

NCS

SCLK

ignored

functional

depends on

NCS

MOSI

ignored

functional

depends on

NCS

XY_LED

undefined

functional

MOTION

undefined

functional

SHTDWN

must be low

functional

State of Signal Pins After VDD is Valid

SHTDWN active

NCS

Functional*

MISO

Undefined

SCLK

Undefined

MOSI

Undefined

XY_LED

Low current

MOTION

Undefined

ADNS3040 Scheda tecnica(PDF) 14 Page - Agilent(Hewlett-Packard)

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