ALXD800EEXJ2VD AMD (ADVANCED MICRO DEVICES), ALXD800EEXJ2VD Datasheet - Page 358

• 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

6.6.18.6 VGA Character Map Select
Index
Type
Reset Value
Character Map A (bits [5,3:2]) and Character Map B (bits [4,1:0]) determine which font tables are used when displaying a
character in text mode. When bit 3 of the character's attribute = 1, Character Map A is used; when bit 3 of the character's
attribute = 0, Character Map B is used. The font tables are stored in the 64 KB in map 2. There are eight font tables. The
character map codes select the font tables as shown in Table 6-52.
6.6.18.7 VGA Memory Mode
Index
Type
Reset Value
358
Bit
7:6
3:2
1:0
Bit
7:4
5
4
3
2
1
0
Code
0
1
2
3
Name
RSVD
CHAR_AZ
CHAR_BZ
CHAR_A
CHAR_B
Name
RSVD
CHAIN4
CHAIN2
EXT_MEM
RSVD
03h
R/W
xxh
04h
R/W
02h
Font Table Location in Map 2
33234C
VGA Character Map Select Register Bit Descriptions
8 KB Block 0
8 KB Block 2
8 KB Block 4
8 KB Block 6
Description
Reserved. Write as read.
Character Map A bit 2.
Character Map B bit 2.
Character Map A bits 1:0.
Character Map B bits 1:0.
Description
Reserved.
Chain4. When set to a 1, CPU address bits 1 and 0 are used to select the map or plane
in the frame buffer DWORD. For example, if CPU A1:A0 = 3, then map 3 is selected. If
CPU A1:A0 = 1, then map 1 is selected. If Chain4 is 0, then the frame buffer addressing
is controlled by the CHAIN2 (bit 2).
Chain2. When set to a 0, CPU address bit 0 selects between frame buffer maps 0 and 1,
or maps 2 and 3, depending on the value in the graphics controller Read Map Select field
(Index 04h[1:0]). For example, if CPU A0 is 0, then map 0 (or 2) is selected.
Extended Memory. This bit should always be set to a 1. It is a throwback to EGA where
the standard frame buffer size was 64 KB and was upgradeable to 256 KB. VGA always
has (at least) 256 KB.
Reserved.
VGA Memory Mode Register Bit Descriptions
Table 6-52. Font Table
Code
4
5
6
7
Display Controller Register Descriptions
AMD Geode™ LX Processors Data Book
Font Table Location in Map 2
8 KB Block 1
8 KB Block 3
8 KB Block 5
8 KB Block 7