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PDF ZR36050PQC-21 Data sheet ( Hoja de datos )
| Número de pieza | ZR36050PQC-21 | |
| Descripción | JPEG IMAGE COMPRESSION PROCESSOR | |
| Fabricantes | ETC | |
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ZR36050
ADVANCE INFORMATION
JPEG IMAGE COMPRESSION PROCESSOR
FEATURES
s Implements JPEG Baseline image compression and
expansion, including:
- DCT/IDCT operations
- Quantization
- Variable length coding/decoding
s Full support of the JPEG Baseline standard, including:
- Bit and byte stuffing
- JPEG markers including restart (RST), application (APP),
and comment (COM)
s JPEG Lossless compression and expansion
s DMA/SLAVE bus interface
s Motion video (30 frames/sec) compression/expansion
capability for CCIR resolution (720 x 480)
s “Fast Preview” option
- Preview of “thumbnail” version of images (up to 25x faster)
s Bit rate control option
- Guarantees compressed image file size
s Low cost solution
- Low cost single chip
- Support for inexpensive memories
- Requires minimal host intervention
s TTL compatible
s 27 and 21 MSamples/sec data-rate
s Standby mode for very low power consumption
s 100-pin plastic quad flat-pack (PQFP) packaging
APPLICATIONS
s Computer and multimedia add-in boards
s Full-motion video compression/expansion
s Digital still cameras and peripherals
s Security and industrial systems
s Videophones and color FAX machines
s Color printers and scanners
s Fixed bit rate image transmission devices
s Cost-sensitive image compression systems
GENERAL DESCRIPTION
The ZR36050 is a high-speed JPEG Image Compression Pro-
cessor that performs the algorithm specified by the JPEG
Baseline and JPEG Lossless standards for high-quality image
compression and expansion of continuous-tone color or mono-
chrome images. The ZR36050 performs Discrete Cosine
Transform (DCT), quantization and variable-length encoding for
image compression (coding), and the corresponding inverse
operations for expansion (decoding).
In the JPEG Baseline encoding operation, the ZR36050
performs the DCT operation on 8 x 8 blocks of image data, con-
verting image data into its spatial frequency components, and
quantizes them using a user defined “quantization table.”
Because the human visual system is less sensitive at the higher
spatial frequencies, these higher frequency components can be
quantized more coarsely than the lower-frequency components,
with negligible effect on image quality.
The coarser quantization of high-frequency coefficients results in
long strings of zero valued quantized coefficients, when the 8x8
blocks are scanned in zigzag order. The scanned coefficients
are characterized in terms of their nonzero values and the zero
run lengths. As a result, a long string of zeroes is coded as a
single number. The ZR36050 then performs Huffman coding
using user-defined Huffman tables, whereby bit patterns of dif-
ferent lengths code the nonzero values (values that occur
frequently use the shortest codes; while those that infrequently
occur use the longest codes). These techniques greatly reduce
the amount of memory needed to store an image.
In the decoding operation, the compressed data is decoded (the
inverse of the Huffman and the zigzag modified-run-length
coding), and dequantized. A 2-D inverse Discrete Cosine Trans-
form is performed on the DCT coefficients, resulting in an
expanded image.
+5V
PIXEL
Interface
Control
DCT
Coefficient
Output
Clock
12
PIXEL
8
CODE
DSYNC
EOS
STOP
COMP
RESET
STDBY
FREEZE
ZR36050
END
2 CL
JPEG IMAGE
COMPRESSION
PROCESSOR
CLKEN
11
COEF
CSYNC
CLK_IN
VSS
COE
CWE
CCS
CAEN
CBUSY
DATA
ADDR
RD
WR
CS
INT
DINT
DREQ
DACK
8
10
Compressed
Data Interface
Host Interface
Figure 1. ZR36050 Logical Pinout
ZORAN Corporation s 1705 Wyatt Drive s Santa Clara, CA 95054 s (408) 986-1314 s FAX (408) 986-1240
August 1993
This document was created with FrameMaker 4.0.4
1 page  
ADVANCE INFORMATION
ZR36050
Table 1. Signal Description1, 2 (Continued)
Type3
Signal
Encode Decode
Description
DSYNC
I O Data Synchronization. This active- low signal is an input in encoding and output in decoding modes.
In the encoding modes, DSYNC marks the start of an 8x8 image data block and should appear as an
input one CLK_IN before the first image data of a block. In the decoding modes, DSYNC is output
one CLK_IN before the first image data sample of a block. The width of DSYNC is one CLK_IN cycle.
In the Fast Preview mode, and the Lossless encoding and decoding modes, this signal precedes
each image data sample.
EOS
I O End Of Scan. This active-low signal is an input in encoding modes. EOS indicates the last image data
sample of each scan entering the ZR36050. In encoding modes, EOS must be input regardless of the
STOP signal.
EOS is an output signal in the decoding mode. It is generated together with the last image data
sample of each scan leaving the ZR36050. In this case, DSYNC will not be issued.
In the Fast Preview and Lossless decoding modes, EOS is output within 64 CLK_IN cycles after the
last sample of a scan. It is merely used in as an indication of the completion of the current process
without having any timing significance.
In decoding mode, EOS is output regardless of the STOP signal.
The width of EOS is one CLK_IN cycle.
COEF(10-0)
O O Coefficient Bus. This 11-bit output bus is used to transfer DCT coefficients out of the device in the
encoding and decoding modes. The DCT coefficients are output in column-major order. This bus is
not used in the Fast Preview and Lossless encoding and decoding modes.
CSYNC
O O Coefficient Synchronization. This active-low signal indicates the beginning of an 8x8 DCT coefficient
block.
In the encoding and decoding modes, this signal is generated by the ZR36050. It is asserted one
CLK_IN cycle before the first coefficient of a block is placed on the COEF bus by the ZR36050. The
width of CSYNC is one CLK_IN cycle.
CSYNC is not used in the Fast Preview and Lossless encoding and decoding modes.
CODE(7-0)
O I Code. In Master mode Compressed Data Transfer, this 8-bit bidirectional bus is used to read the com-
pressed data from or write to the Compressed Data Memory.
In the 16-bit Slave and DMA modes, this bus is used as an extension of the DATA bus.
COE
- O Compressed Data Memory Read. This active-low output signal acts as a read pulse from the
ZR36050 to the Compressed Data Memory. COE goes active 0.5 CLK_IN cycles after the start of a
read cycle and remains active until the end of the read cycle. The CODE bus is latched on the rising
edge of COE.
CWE
O - Compressed Data Memory Write. This active-low output signal acts as a write pulse from the
ZR36050 to the Compressed Data Memory. CWE goes active 0.5 CLK_IN cycles after the start of a
write cycle and remains active until the end of the write cycle.
CCS
O O Compressed Data Memory Chip Select. This active-low output signal acts as a chip select signal from
the ZR36050 to the Compressed Data Memory. CCS goes active at the start of a read or write cycle
and remains active throughout the cycle. CCS remains active continuously in back to back read or
write cycles. The length of a read or write cycle can be from one to eight CLK_IN periods.
CAEN
O O Address Counter Enable. This active-low output signal can be used to advance an external Com-
pressed Data Memory address counter.
1. The DATA, CODE, PIXEL, and COEF buses have internal pull-downs that provide 50 microamps of pull-down current at 0.4 volts.
2. The control pins: DSYNC, EOS, STOP, END, CL, CSYNC, COE, CWE, CCS, CAEN, INT, DINT, DREQ and COMP, have internal pull-up
devices that provide 50 microamps at 2.4 volts. These pull-ups are turned on only when STDBY is active but RESET is inactive. When STDBY
is active together with RESET, the above control pins float.
3. I = Input, O = Output, B = Bidirectional, S = Supply.
5
5 Page 
ADVANCE INFORMATION
ZR36050
Memory, however, does impose some restrictions, that have
only a very minor effect on the applicability of the device:
s The number of image components specified in the frame
header must be eight or fewer.
s A DHT marker segment must have a length of 420 or fewer
bytes (excluding the DHT marker), otherwise the tables may
be decoded incorrectly into the Huffman Table Store.
A JPEG Baseline DHT segment has a length of only 418
bytes, so this is not normally a problem. The restriction, how-
ever, stems from the fact that the standard does not explicitly
disallow the repetition of the same tables in a DHT segment.
s A DQT marker segment of any length is decoded correctly
into the Quantization Tables Store. If, however, its length
(excluding the DQT marker) is greater than 262 bytes, it may
overwrite the DHT, APP, and COM segments in Internal
Memory, affecting the ability of the host to read out the
contents of these segments correctly.
A JPEG Baseline DQT segment has a maximum length of
262 bytes. The restriction again stems from the fact that the
standard does not explicitly disallow the repetition of the
same tables in a DQT segment.
In addition to the above restrictions, to be decoded correctly, the
frame header of a JPEG Lossless compressed image must
specify a precision of 12 or fewer bits, and only horizontal sub-
sampling. The scan header must select a type 1 predictor (one-
dimensional horizontal), and can specify at most two different
Huffman tables.
OPERATING MODES
The host sets the operating mode of the ZR36050 by program-
ming the MODE register. Nine distinct modes can be selected,
falling into two categories:
s six encoding modes, involving compression and associated
functions. The encoding modes are: JPEG Baseline
Compression Pass, Auto Bit Rate Control, Statistical Pass,
Compression Pass with Bit Rate Control, Tables-only Pass,
and Tables Preload.
s three decoding modes, involving expansion: JPEG
Baseline Expansion, Fast Preview, and Tables Preload.
Two additional modes, the Lossless compression and expansion
modes of operation, are not distinguished from the JPEG
Baseline Compression Pass and Expansion, respectively, in the
programming of the MODE register. Rather, the ZR36050 enters
the JPEG Baseline or Lossless mode based on the SOF (Start
Of Frame) marker. If the marker found in internal memory (com-
pression) or the compressed data (expansion) is SOF0 (FFC0),
the ZR36050 configures itself for JPEG Baseline operation. Oth-
erwise, if the marker is SOF3 (FFC3), it configures itself for
Lossless operation.
Auto Bit Rate Control, Statistical Pass, and Compression Pass
with Bit Rate Control are relevant only to JPEG Baseline com-
pression, and Fast Preview is useful only with JPEG Baseline
compressed data. These modes have no meaning for Lossless
operation.
ENCODING MODES
JPEG Baseline Compression Pass
The Compression Pass performs the Baseline encoding opera-
tion on the input image component samples. During a
Compression Pass, the ZR36050 reads the JPEG marker
segment information written by the host in the Marker Segments
Section of Internal Memory, and uses it to determine the MCU
configuration, and includes the compulsory and optional marker
segments (selected by the MARKERS_EN register) in the com-
pressed data stream. Note that, if the DQT marker segment is
enabled, the ZR36050 first multiplies the quantization tables
specified in the DQT segment of Internal Memory by the Scale
Factor, and stores the scaled tables in the Quantization Table
Store. The quantization tables included in the compressed data
are the same as the stored (scaled) tables. At the completion of
the JPEG Baseline Compression Pass, the ZR36050 calculates
a New Scale Factor (NSF) and saves it in the SF Internal
Memory register. The NSF can be used in the next encoding
operation or the host can overwrite it by its own Scale Factor.
Statistical Pass
In the Statistical Pass, the ZR36050 performs the computations
for JPEG Baseline encoding of the image, with the initially spec-
ified Scale Factor, but without transferring any data to the Code
Buffer. It accumulates the code volume and a total activity
measure. Based on the Target Code Volume (TCV_DATA regis-
ter), it calculates the Allocation Factor and a new Scale Factor at
the end of the pass. It writes the new Scale Factor in the SF reg-
ister, in place of the initial Scale Factor, and the Allocation
Factor, Accumulated Code Volume, and Total Activity measure,
in their respective registers (SF, AF, ACV, and ACT), where the
host can access them if needed.
Compression Pass with Bit Rate Control
This mode allows the user to ensure a compressed data volume
equal to or slightly less than the Target Code Volume. Before
encoding each block, the ZR36050 computes a measure of the
block activity, and allocates a code volume to the block based on
the activity and the Allocation Factor (AF register). During
encoding of the block, if the accumulated code volume for the
block exceeds the allocation, the ZR36050 truncates the code
for the block. The code is also truncated if it exceeds the
Maximum Block Code Volume specified in the MBCV register.
Aside from the bit rate control, this mode is the same as a JPEG
11
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