Datasheet

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MT9D111__2_REV5.fm - Rev. B 2/06 EN
22 ©2004 Micron Technology, Inc. All rights reserved.
MT9D111 - 1/3.2-Inch 2-Megapixel SOC Digital Image Sensor
Architecture Overview
Micron Confidential and Proprietary
can provide 30 fps image input for the display and simultaneously translate user com-
mands received via two-wire serial interface into digital waveforms driving the lens
actuator.
Lens Actuator Interface
Actuators used to move lenses in AF cameras can be classified into several broad catego-
ries that differ significantly in their requirements for driving signals. These requirements
also vary from one device to another within each category. To ensure its compatibility
with many different actuators, the MT9D111 includes a general purpose input/output
module (GPIO).
In essence, the GPIO is a programmable rectangular waveform generator, with 12 indi-
vidually controllable output pads (GPIO0 through GPIO11), a separate power supply pad
(V
DDGPIO), and a separate clock domain that can be disconnected from the master
clock to save power when the GPIO is not in use. The GPIO can toggle its output pads as
fast as half the master clock frequency (every 25ns at 80 MHz).
An external host processor and the embedded microcontroller (MCU) of the MT9D111
have two ways to control the voltages on the GPIO output pads:
1. Setting or clearing bits in a control register
The state of the GPIO pads is updated immediately after writing to the register is fin-
ished. Since writing via the two-wire serial interface takes some time, this way does
not give the host processor a very precise control over GPIO output timing.
2. Waveform programming
The second way to obtain a desired output from the GPIO is to program into its regis-
ters a set of periodic waveforms and initialize their generation. The GPIO then gener-
ates the programmed waveforms on its own, without waiting for any further input,
and therefore with the best attainable timing precision. If necessary, the GPIO can
notify the MCU and the host processor about reaching certain points in the wave-
forms generation, e.g., the end of a particular waveform. Every GPIO notification has
two components: the GPIO sends a wakeup signal to the MCU and sets a bit in its sta-
tus register that can be polled by the MCU and/or the host processor. The wakeup sig-
nals have an effect only when the MCU is in sleep mode.
The MT9D111 can be set up not only to output digital signals to a lens actuator and/or
other similar devices, but also to receive their digital and analog feedback. All GPIO out-
put pads are reconfigurable as high-impedance digital inputs. The logical state of each
GPIO pad is mirrored by the state of a bit in a dedicated register, which allows the MCU
and host processor to sample digital input signals at intervals equal to their respective
register read times. Analog input signals (0.1V to 1.0V) can be sampled using one of the
10-bit ADCs in the sensor core. During horizontal blanking periods, when it does not
digitize the sensor signal, this ADC samples voltages on AIN1, AIN2, and AIN3 input
pads. The results are stored in dedicated registers. The maximum signal sampling rate
permitted by this scheme is about 36000 samples per second.
Context and Operational Modes
The MT9D111 can operate in several modes, including preview, still capture (snapshot),
and video. All modes of operation are individually configurable and are organized as two
contexts—context A and context B. A context is defined by sensor image size, frame rate,
resolution and other associated parameters. The user can switch between the two con-
texts by sending a command via the two-wire serial interface.