AMD Geode™ LX Processors Data Book 259
Graphics Processor Register Definitions 33234H
6.4.2 Graphics Processor Configuration Registers
6.4.2.1 Destination Offset (GP_DST_OFFSET)
GP_DST_OFFSET is used to give a starting location for the destination of a BLT or vector in the destination region of mem-
ory. It consists of three fields, the OFFSET, XLSBS and YLSBS. The OFFSET is a pointer, which when added to the desti-
nation base address, gives the memory address of the first byte of the BLT or vector. For a left-to-right direction BLT or a
vector, the address should be aligned to the least significant byte of the first pixel, since this is the leftmost byte. For a right-
to-left direction BLT, the address should be aligned to the most significant byte of the first pixel, since this is the rightmost
byte of the BLT. The address alignment must also be correct with respect to the pixel depth. In 32-bpp mode, the address
specified must be aligned to the least significant or most significant byte of a DWORD, depending upon BLT direction. Pix-
els may not straddle a DWORD boundary. In 16-bpp mode, the address specified must be aligned to a 16-bit boundary. The
XLSBS and YLSBS are used to inform the hardware of the location of the pixel within the pattern memory for pattern align-
ment.
6.4.2.2 Source Offset (GP_SRC_OFFSET)
GP_SRC_OFFSET is used during a BLT to give a starting location for the source in the source region of memory. In this
mode, the register consists of two fields, the OFFSET and XLSBS. The OFFSET is a pointer, which when added to the
source base address, gives the memory location of the byte containing the first pixel of the BLT. As in the destination offset,
this value must be aligned correctly for BLT direction and pixel depth. When host source data is used, the two LSBs of the
OFFSET must still be initialized with the byte location of the first source pixel in the host source data stream. The XLSBs
are used when the source is monochrome to give an offset within the specified byte to the bit representing the starting pixel.
In byte-packed mode, the XLSBs are used to index into the first byte of every new line of source data. In unpacked mode,
both the OFFSET and XLSBs are used to index into the first DWORD of every new line of source data.
GP Memory Offset 00h
Type R/W
Reset Value 00000000h
GP_DST_OFFSET Register Map
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
YLSBS XLSBS RSVD OFFSET
GP_DST_OFFSET Bit Descriptions
Bit Name Description
31:29 YLSBS Y LSBs. Indicates Y coordinate of starting pixel within pattern memory.
28:26 XLSBS X LSBs. Indicates X coordinate of starting pixel within pattern memory.
25:24 RSVD Reserved. Write as read.
23:0 OFFSET Offset. Offset from the destination base address to the first destination pixel.
GP Memory Offset 04h
Type R/W
Reset Value 00000000h
GP_SRC_OFFSET Register Map
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSVD XLSBS RSVD OFFSET
GP_SRC_OFFSET Bit Descriptions
Bit Name Description
31:29 RSVD Reserved. Write as read.
28:26 XLSBS X LSBs. Offset within byte to first monochrome pixel.