ADNS-2030 Avago Technologies US Inc., ADNS-2030 Datasheet - Page 20

• Manufacturer Part Number: ADNS-2030
• Description: Optical Mouse Sensor,DIP
• Manufacturer: Avago Technologies US Inc.

Specifications of ADNS-2030

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Notes on Power up and the Serial Port
The sequence in which V
during powerup can affect the operation of the serial
port. The diagram below shows what can happen shortly
after powerup when the microprocessor tries to read data
from the serial port.
This diagram shows the V
point the microcontroller starts its program, sets the SCLK
and SDIO lines to be outputs, and sets them high. It then
waits to ensure that the ADNS-2030 has powered up and
is ready to communicate. The microprocessor then tries
to read from location 0x00, Product_ID, and is expecting
a value of 0x03. If it receives this value, it then knows that
the communication to the ADNS-2030 is operational.
The problem occurs if the ADNS-2030 powers up before
the microprocessor sets the SCLK and SDIO lines to be
Figure 34. Power up serial port sequence.
0
SCLK
SDIO
V
PD
DD
DD
DD
, PD, SCLK and SDIO are set
rising to valid levels, at some
Problem Area
Address 0x00
outputs and high. The ADNS-2030 sees the raising of the
SCLK as a valid rising edge, and clocks in the state of the
SDIO as the first bit of the address (sets either a read or a
write depending upon the state).
In the case of SDIO low, then a read operation has
started. When the microprocessor begins to actually
send the address, the ADNS-2030 already has the first bit
of an address. When the 7
ADNS-2030 has a valid address, and drives the SDIO line
high within 120 ns (see detail “A” in Figure 26 and Figure
27). This results in a bus fight for SDIO. Since the address
is wrong, the data sent back will be incorrect.
In the case of SDIO high, a write operation is started. The
address and data are out of synchronization, and the
wrong data will be written to the wrong address.
Data 0x03
th
bit is sent by the micro, the