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AMD Geode™ LX Processors Data Book 325
Display Controller Register Descriptions
33234H
6.6.4.8 DC Line Size (DC_LINE_SIZE)
This register specifies the number of bytes to transfer for a line of frame buffer, compression buffer, and video buffer data.
The compressed line buffer is invalidated if it exceeds the CB_LINE_SIZE (bits [18:12]).
Settings written to this register do not take effect until the start of the following frame or interlaced field.
DC_DV_TOP Bit Descriptions
Bit Name Description
31:24 RSVD Reserved. These bits should be programmed to zero.
23:10 DV_TOP_ADDR Dirty/Valid Region Top Address. When enabled via bit 0 (DV_TOP_EN), this field indi-
cates the size of the region to be watched for frame buffer accesses. When writes to this
region occur and the compression logic is in frame-dirty mode, the frame is marked as
dirty. (Writes outside this region, regardless of the settings in the DV_CTL register (DC
Memory Offset 088h), do not cause the frame to be marked as dirty in frame-dirty mode.)
The bits in this field correspond to address bits [23:10].
9:1 RSVD Reserved. These bits should be programmed to zero.
0 DV_TOP_EN Dirty/Valid Region Top Enable. This bit enables the top-of-region check for frame-dirty
mode. This bit should be cleared if the compression logic is NOT configured for frame-
dirty mode.
DC Memory Offset 030h
Typ e R /W
Reset Value xxxxxxxxh
DC_LINE_SIZE Register Map
313029282726252423222120191817161514131211109876543210
RSVD VID_LINE_SIZE
RSVD
CB_LINE_SIZE RSVD FB_LINE_SIZE
DC_LINE_SIZE Bit Descriptions
Bit Name Description
31:30 RSVD Reserved. These bits should be programmed to zero.
29:20 VID_LINE_SIZE Video Line Size. This value specifies the number of QWORDs (8-byte segments) to
transfer for each source line from the video buffer in YUV 4:2:2 mode. In YUV 4:2:0
mode, it specifies the number of QWORDs to transfer for the U or V stream for a source
line (2x this amount is transferred for the Y stream). In YUV 4:2:2 mode, this field must be
set to a multiple of four QWORDs -- bits [21:20] must be 0.
19 RSVD Reserved. This bit should be programmed to zero.
18:12 CB_LINE_SIZE Compressed Display Buffer Line Size. This value represents the number of QWORDs
for a valid compressed line plus 1. It is used to detect an overflow of the compressed
data FIFO. When the compression data for a line reaches CB_LINE_SIZE QWORDs, the
line is deemed incompressible. Note that DC actually writes CB_LINE_SIZE + 4
QWORDs to memory, so if X QWORDs are allocated for each compression line, then
X - 4 + 1 (or X - 3) should be programmed into this register. Note also that the
CB_LINE_SIZE field should never be larger than 65 (041h) since the maximum size of
the compressed data FIFO is 64 QWORDs.
11:10 RSVD Reserved. These bits should be programmed to zero.
9:0 FB_LINE_SIZE Frame Buffer Line Size. This value specifies the number of QWORDs (8-byte seg-
ments) to transfer for each display line from the frame buffer.