Datasheet

PDF: 09005aef8202ec2e/Source: 09005aef8202ebf7 Micron Technology, Inc., reserves the right to change products or specifications without notice.
MT9D111__6_REV5.fm - Rev. B 2/06 EN
113 ©2004 Micron Technology, Inc. All rights reserved.
MT9D111 - 1/3.2-Inch 2-Megapixel SOC Digital Image Sensor
Output Format and Timing
Micron Confidential and Proprietary
The "continuous" and spoof JPEG output modes differ primarily in how the LINE_VALID
output is asserted. In the continuous mode, LINE_VALID is asserted only during output
clock cycles containing valid JPEG data. The resulting LINE_VALID signal pattern is non-
uniform and highly image dependent, reflecting the inherent nature of JPEG data
stream. In the spoof mode, LINE_VALID is asserted and de-asserted in a more uniform
pattern emulating uncompressed video output with horizontal blanking intervals. When
LINE_VALID is de-asserted, available JPEG data are not output, but instead remain in
the FIFO until LINE_VALID is asserted again. During the time when LINE_VALID is
asserted, the output clock is gated off whenever there is no valid JPEG data in the FIFO.
Note: As a result, spoof “lines” containing the same number of valid data bytes may be out-
put within different time intervals depending on constantly varying JPEG data rate.
The host processor configures the spoof pattern by programming the total number of
LINE_VALID assertion intervals, as well as the number of output clock periods during
and between LINE_VALID assertions. In other words, the host processor can define a
temporal “frame” for JPEG output, preferably with “size” tailored to the expected JPEG
file size. If this frame is too large for the total number of JPEG bytes actually produced,
the MT9D111 either de-asserts FRAME_VALID or continues to pad unused “lines” with
zeros until the end of the frame. If the frame is too small, the MT9D111 either continues
to output the excess JPEG bytes until the entire JPEG compressed image is output or dis-
cards the excess JPEG bytes and sets an error flag in a status register accessible to the
host processor.
In the continuous output mode, the JPEG output clock can be configured to be either
gated off or running while LINE_VALID is de-asserted. To save extra power, the JPEG out-
put clock can also be gated off between frames (when FRAME_VALID is de-asserted) in
both continuous and spoof output mode. In the continuous output mode, there is an
option to insert JPEG SOI (0xFFD8) and EOI (0xFFD9) markers respectively before and
after valid JPEG data. SOI and EOI can be inserted either inside or outside the
FRAME_VALID assertion period, but always outside LINE_VALID assertions.
The output order of even and odd bytes of JPEG data can be swapped in the spoof output
mode. This option is not supported in the continuous mode.
Output clock speed can optionally be made to vary according to the fullness of the FIFO,
to reduce the likelihood of FIFO overflow. When this option is enabled, the output clock
switches at three fixed levels of FIFO fullness (25 percent, 50 percent and 75 percent) to a
higher or lower frequency, depending on the direction of fullness change. The set of pos-
sible output clock frequencies is restricted by the fact that its period must be an integer
multiple of the master clock period. The frequencies to be used are chosen by program-
ming three output clock frequency divisors in registers R14:2 and R15:2. Divisor N1 is
used if the FIFO is less than 50 percent full and last fullness threshold crossed has been
25 percent. When the FIFO reaches 50 percent and 75 percent fullness, the output clock
switches to divisor N2 and N3, respectively. When the FIFO fullness level drops to 50 per-
cent and 25 percent, the output clock is switched back to divisor N2 and N1, respectively.
The host processor can read registers containing JPEG status flags and JPEG data length
(total byte count of valid JPEG data) via a two-wire serial interface. In addition, the JPEG
data length and JPEG status byte are always appended at the end of JPEG spoof frame.
JPEG status byte can be optionally appended at the end of JPEG continuous frame. JPEG
data stream sent to the host does not have a header.