PixArt Imaging Inc.
ADNS-7550 Integrated Molded Lead-Frame DIP Sensor
Motion Pin Timing
VCSEL’s Typical Characteristics
The motion pin is a level-sensitive output that signals the
micro-controller when motion has occurred. The motion
pin is lowered whenever the motion bit is set; in other
words, whenever there is data in the Delta_X or Delta_Y
registers. Clearing the motion bit (by reading Delta_X
and Delta_Y, or writing to the Motion register) will put
the motion pin high.
2.5
V = C
2.0
V = A,V
1.5
1.0
0.5
0.0
LASER Mode
For power savings, the VCSEL will not be continuously on.
ADNS-7550 will flash the VCSEL only when needed.
0
2
4
6
8
10
Synchronous Serial Port
Forward Current, IF (mA)
The synchronous serial port is used to set and read pa-
rameters in the ADNS-7550, and to read out the motion
information. The port is a four-wire port. The host
micro-controller always initiates communication; the
ADNS-7550 never initiates data transfers. SCLK, MOSI,
and NCS may be driven directly by a micro-controller.
The port pins may be shared with other SPI slave devices.
When the NCS pin is high, the inputs are ignored and the
output is tri-stated.
Figure 12. Forward Voltage vs. Forward Current for VCSEL
50
V = C
V = A,V
40
30
20
10
0
The lines that comprise the SPI port:
SCLK: Clock input. It is always generated by the master
(the micro-controller).
MOSI: Input data. (Master Out/Slave In)
MISO: Output data. (Master In/Slave Out)
10
9
11 12 13 14 15
0
1
2
3
4
5
6
7
8
Forward Current, IF (mA)
NCS:
Chip select input (active low). NCS needs to be low
to activate the serial port; otherwise, MISO will be
high Z, and MOSI & SCLK will be ignored. NCS can
also be used to reset the serial port in case of an
error.
Figure 13. Junction Temperature Rise vs. Forward Current for VCSEL
Chip Select Operation
The serial port is activated after NCS goes low. If NCS
is raised during a transaction, the entire transaction is
aborted and the serial port will be reset. This is true for
all transactions. After a transaction is aborted, the normal
address-to-data or transaction-to-transaction delay is
still required before beginning the next transaction. To
improve communication reliability, all serial transac-
tions should be framed by NCS. In other words, the port
should not remain enabled during periods of non-use
because ESD and EFT/B events could be interpreted as
serial communication and put the chip into an unknown
state. In addition, NCS must be raised after each burst-
mode transaction is complete to terminate burst-mode.
The port is not available for further use until burst-mode
is terminated.
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
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PIXART [ PIXART IMAGING INC. ]
