MT9D011 datasheet(21/61 Pages) MICRON

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MT9D011

2-MEGAPIXEL DIGITAL IMAGE SENSOR

PRELIMINARY

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Micron Technology, Inc., reserves the right to change products or specifications without notice.

MT9D011__MI2010_E_2.fm - Rev. A 11/04 EN

Table 7 provides a detailed description of the regis-

ters. Bit fields that are not identified in the table are

read only.

Double-Buffered Registers

Some sensor settings cannot be changed during

frame readout. For example, changing row width

Reg0x03 part way through frame readout results in

inconsistent LINE_VALID behavior. To avoid this, the

MT9D011 double buffers many registers by imple-

menting a “pending” and a “live” version. Reads and

writes access the pending register. The live register

controls the sensor operation.

The value in the pending register is transferred to a

live register at a fixed point in the frame timing, called

“frame start.” Frame start is defined as the point at

which the first dark row is read out. By default, this

occurs ten row times before FRAME_VALID goes high.

Reg0x22 enables the dark rows to be shown in the

image, but this has no effect on the position of frame

start.

To determine which registers or register fields are

double-buffered in this way, see Table 7, the “sync’d-

to-frame-start” column.

Reg0x0D[15] can be used to inhibit transfers from

the pending to the live registers. This control bit

should be used when making many register changes

that must take effect simultaneously.

Bad Frames

A bad frame is a frame where all rows do not have

the same integration time, or where offsets to the pixel

values changed during the frame.

Many changes to the sensor register settings can

cause a bad frame. For example, when row width

Reg0x03 is changed, the new register value does not

affect sensor behavior until the next frame start. How-

ever, the frame that would be read out at that frame-

start has been integrated using the old row width. Con-

sequently, reading it out using the new row width

results in a frame with an incorrect integration time.

default,

most

bad

frames

are

masked:

LINE_VALID and FRAME_VALID are inhibited for

these frames so that the vertical blanking time

between frames is extended by the frame time.

To determine which register or register field

changes can produce a bad frame, see Table 7, the

“bad frame” column, and these notations:

• N—No. Changing the register value does not

produce a bad frame.

• Y—Yes. Changing the register value might produce a

bad frame.

• YM—Yes; but the bad frame is masked out unless

the “show bad frames” feature (Reg0x0D[8]) is

enabled.

Changes to Integration Time

If the integration time (Reg0x09) is changed while

FRAME_VALID is asserted for frame n, the first frame

output using the new integration time is frame (n+2).

The sequence is as follows:

1. During frame n, the new integration time is held

in the Reg0x09 pending register.

2. At the start of frame (n+1), the new integration

time is transferred to the Reg0x09 live register.

Integration for each row of frame (n+1) has been

completed using the old integration time. The earliest

time that a row can start integrating using the new

integration time is immediately after that row has been

read for frame (n+1). The actual time that rows start

integrating using the new integration time is depen-

dent on the new value of the integration time.

3. When frame (n+1) is read out, it is integrated

using the new integration time.

If the integration time is changed (Reg0x09 written)

on successive frames, each value written is applied to a

single frame; the latency between writing a value and it

affecting the frame readout remains at two frames.

Changes to Gain Settings

When

the

gain

settings

(Reg0x2B,

Reg0x2C,

Reg0x2D, Reg0x2E, and Reg0x2F) are changed, the gain

is usually updated on the next frame start. When the

integration time and the gain are changed simulta-

neously, the gain update is held off by one frame so

that the first frame output with the new integration

time also has the new gain applied.

MT9D011 Datasheet(PDF) 21 Page - Micron Technology

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