SH7785 Datasheet, PDF (1057/1692 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

20. Graphics Data Translation Accelerator (GDTA)
No. Operation
(7) IDCT data
reading
Description
IDCT data stored in buffer RAM 1 is read.
(Only blocks specified by a CBP setting of 1 are read from buffer RAM 1.)
The IDCT data should be stored in buffer RAM 1 as 16-bit signed data.
(The sign is discriminated using the uppermost bit (bit 15).)
Regardless of the CBP value, the IDCT data should be stored in successive
addresses in the order Y0 (128 bytes), Y1 (128 bytes), Y2 (128 bytes), Y3
(128 bytes), U (128 bytes), V (128 bytes).
When there is a CBP=0 block, the address space should not be packed, but
data should be stored in successive addresses in the Y0, Y1, Y2, Y3, U, V
data format.
The CBP value indicates whether a sign is required compared with the
comparison image for the six blocks (four luminance blocks and two
chrominance blocks). The above Y0, Y1, Y2, Y3, U, V are CBP values of
block positions in the following format.
CBP Blocks with YUV4:2:0
Y0 Y1
Luminance Y _{Y2 Y3}
Chrominance U
U/V _V
(8) Estimated
image data
generation
(9) Estimated
image data
writing
(Data for a CBP=0 block: data invalid)
9-bit saturation computation is performed for IDCT data read from RAM 1 (-
256 ≤ x ≤ 255).
(The sign is discriminated using the uppermost bit (bit 15).)
IDCT data reading is performed in parallel with the operation of (5) and (6).
Estimated image data is generated using the following formula from the half-
pixel processing data generated in (6) and the IDCT data (9-bit data after
saturation computation) read in (7).
Formula: (data of (6) + data of (7)) -> (saturation computation) (0 ≤ x ≤ 255)
Estimated image data is written to DDR2-SDRAM at the address computed in
(1) and (2).
(2) MC Processing Procedure
The CPU performs required initialization and starts the processing. IDCT data must be prepared in
the buffer RAM 1. The procedure is shown below.
Rev.1.00 Jan. 10, 2008 Page 1027 of 1658
REJ09B0261-0100