AT77C104B datasheet(24/36 Pages) ATMEL

24 / 36 page

AT77C104B

5347B–BIOM–08/04

Example of Navigation

Registers

Figure 12 represents a typical reading sequence of the three navigation registers.

Refer to “Appendix C” on page 34 for flowchart

Figure 12. Reading of the Navigation Registers

Image Capture (Fast SPI)

This serial interface enables full-speed acquisition of the sensor’s pixels by the host.

This interface only supports the serial clock (SCK) and one data line: MISO (Master In/

Slave Out).

Communication Protocol When the sensor is in acquisition mode, the host can receive pixels through the fast SPI

(FSS/ = 0). The host must transmit the communication clock (SCK) to receive the pixels.

This clock must have a regular frequency to obtain constant fingerprint slices (See “Reg-

istration Integration Time” on page 27).

With the sensor configured to acquisition mode, the controller can proceed to fast

accesses.

Figure 13. Example of an 8-bit Access

During an 8-bit access, the sensor transmits two pixels (each pixel is coded on 4 bits).

SCK

MISO

MOSI

Reading of Navigation

Emission of the First

Navigation Register

(No Overflow, Y Negative Movement

Click Detected, Black Slice)

Emission of the Second

Navigation Register

(X Absolute Movement

= 24 Pixels)

Emission of the Third

Navigation Register

(Y Absolute Movement

= 144 Pixels)

FSS/ = 0

Sending of Dummy Data

0b0000000

Reception of 2 Pixels

End of

Communication

Sending of 2 Pixels (8 Bits)

FSS/ = 1

Yes

Controller

Sensor

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