Rainbow Electronics AT77C105A - Manual (Page 11)

11
AT77C105A [Preliminary]
5419A–BIOM–01/05
Functional Description
The AT77C105A is a fingerprint sensor based on FingerChip technology. It is controlled
by an SPI serial interface through which output data is also transferred (a slow SPI for
the pointing function and a fast one for acquisition). Six modes are implemented:
– Sleep Mode: A very low consumption mode controlled by the reset pin RST.
In this mode, the internal clocks are disabled and the registers are initialized.
– Stand-by Mode: Also a low consumption mode that waits for an action from
the host. The slow serial port interface (SSPI) and control blocks are
activated. In this mode the oscillator can remain active.
– Click Mode: Waits for a finger on the sensor. The SSPI and control blocks
are activated. The local oscillator, the click array and the click block are all
activated.
– Navigation Mode: Calculates the finger’s x and y movements across the
sensor. The SSPI and control blocks are still activated. The local oscillator,
the navigation array and the navigation block are also activated.
– Acquisition Mode: Slices are sent to the host for finger reconstruction and
identification. The SSPI and control blocks are still activated. The fast serial
port interface block (FSPI) and the acquisition array are activated, as well as
the local oscillator when watchdog is required.
– Test: This mode is reserved for factory testing.
In the final application, three main modes are used:
– Stand-by: Low consumption mode
– Pointing: Equivalent to click and navigation modes
– Acquisition: Fingerprint image capture
Note: The term”host” describes the processor (controller, DSP...) linked to the sensor. It is the
master. In the description of n-bit registers (see “Function Registers” on page 13), the
term “b0” describes the Least Significant Bit (LSB). The term “b(n-1)” describes the Most
Significant Bit (MSB). Binary data is written as 0b_ and hexadecimal data as 0x_.