PixArt Imaging Inc.
ADBS-A350 Optical Finger Navigation
Read Operation
A read operation, defined as data going from the ADBS-A350 to the micro-controller, is always initiated by the micro-
controller and consists of two bytes. The first byte contains the address, is sent by the micro-controller over MOSI, and
has a “0” as its MSB to indicate data direction. The second byte contains the data and is driven by the ADBS-A350 over
MISO. The sensor outputs MISO bits on falling edges of SCLK and samples MOSI bits on every rising edge of SCLK.
NCS
SCLK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Cycle #
SCLK
MOSI
0
A6
A5
A4
A3
A2
A1
A0
Do not care
MISO
D0
D7
D6
D5
D4
D3
D2
D1
tSRAD delay
Figure 13. Read Operation
SCLK
NOTE: The 0.5/f
minimum high state of SCLK is also the minimum
SCLK
tHOLD-MISO
MISO data hold time of the ADBS-A350. Since the falling edge of
SCLK is actually the start of the next read or write command, the
ADBS-A350 will hold the state of data on MISO until the falling edge
of SCLK.
tDLY-MISO
MISO
D0
tr-MISO
tf-MISO
Figure 14. MISO Delay and Hold Time
Required timing between Read and Write Commands
There are minimum timing requirements between read and write commands on the serial port.
tSWW
SCLK
Address
Data
Address
Write Operation
Data
Write Operation
Figure 15. Timing between two write commands
If the rising edge of the SCLK for the last data bit of the second write command occurs before the required delay (t
then the first write command may not complete correctly.
),
SWW
tSWR
SCLK
Address
Write Operation
Figure 16. Timing between write and read commands
Data
Address
Next Read
Operation
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PixArt Imaging Inc.
E-mail: fae_service@pixart.com.tw
17
PIXART [ PIXART IMAGING INC. ]
