ALXD800EEXJ2VD AMD (ADVANCED MICRO DEVICES), ALXD800EEXJ2VD Datasheet - Page 374

• Manufacturer Part Number: ALXD800EEXJ2VD
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of ALXD800EEXJ2VD

• Operating Temperature (min): 0C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

6.6.20.7 VGA Read Map Select
Index
Type
Reset Value
6.6.20.8 VGA Graphics Mode
Index
Type
Reset Value
374
Bit
7:2
1:0
Bit
7
6
5
4
3
2
Name
RSVD
R_MP_SL
Name
RSVD
256_CM
SH_R_MD
ODD_EVEN
RD_MD
RSVD
04h
R/W
xxh
05h
R/W
xxh
33234C
Description
Reserved.
Read Map Select. This field specifies which map CPU read data is taken from in read
mode 0. In Odd/Even modes (specified by the Odd/Even bit in the Graphics Mode regis-
ter, Index 05h[4]) bit 1 of this field specifies which pair of maps returns data.
When bit 1 is 0, data is returned from maps 0 and 1. When bit 1 is 1, data is returned from
maps 2 and 3. The CPU read address bit A0 determines which byte is returned (low or
high) in Odd/Even modes. In non-Odd/Even modes, these bits (both bits [1:0]) specify
the map to read (0, 1, 2, or 3) and the CPU accesses data sequentially within the speci-
fied map.
Description
Reserved.
256 Color Mode. When set to a 1, this bit configures the video serializers in the graphics
controller for the 256 color mode (BIOS mode 13h). When this bit is 0, the Shift Register
Mode bit (bit 5) controls the serializer configuration.
Shift Register Mode. When set to a 1, this bit configures the video serializers for BIOS
modes 4 and 5. When this bit is 0, the serializers are taken in parallel (i.e., configured for
4-bit planar mode operation).
Note that the serializers are also wired together serially so that map 3 bit 7 feeds map 2
bit 0, map 2 bit 7 feeds map 1 bit 0, and map 1 bit 7 feeds map 0 bit 0. This allows for a
32-pixel 1 bit-per-pixel serializer to be used. For this configuration, color planes 1, 2, and
3 should be masked off using the Color Plane Enable register (Attribute Controller, Index
12h, on page 379.)
Odd/Even. When this bit is set to 1, CPU address bit A0 will select between maps 0 and
1 or maps 2 and 3 depending on the state of the Read Map Select field (Index 04h[1:0]).
When this bit is 0, the CPU accesses data sequentially within a map. This bit is equiva-
lent to the Odd/Even bit in the VGA Miscellaneous register (Index 06h[2]), but is inverted
in polarity from that bit.
Read Mode. This bit determines what is returned to the CPU when it reads the frame
buffer. When this bit is 1, the result of a color compare operation is returned. The eight
bits in the CPU read data contain a 1 in each pixel position where the color compare
operation was true, and a 0 where the operation was false. When this bit is 0, frame
buffer map data is returned.
Reserved.
VGA Read Map Select Register Bit Descriptions
VGA Graphics Mode Register Bit Descriptions
Display Controller Register Descriptions
AMD Geode™ LX Processors Data Book