PixArt Imaging Inc.
ADBS-A350 Optical Finger Navigation
The synchronous serial port is used to set and read para-
meters in the ADBS-A350, and to read out the motion
information.
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 transactions
should be framed by NCS. In other words, the port should
not remain enabled during periods of non-use because
ESD events could be interpreted as serial communica-
tion 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.
The port is a four wire serial port. The host micro-controller
always initiates communication; the ADBS-A350 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.
The lines that comprise the 4-wire 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)
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.
Write Operation
Write operation, defined as data going from the micro-
controller to the ADBS-A350, is always initiated by the
micro-controller and consists of two bytes. The first byte
contains the address (seven bits) and has a “1” as its MSB
to indicate data direction. The second byte contains the
data. The ADBS-A350 reads MOSI on rising edges of SCLK.
NCS
2
1
3
4
5
6
7
8
9
12
15
16
1
2
10
11
13
14
SCLK
MOSI
A6
A6
A5
A4
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
1
1
Do not care
MISO
MOSI Driven by Micro-Controller
Figure 11. Write Operation
SCLK
MOSI
tHold,MOSI
tsetup , MOSI
Figure 12. MOSI Setup and Hold Time
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
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PIXART [ PIXART IMAGING INC. ]
