User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
R
88
9.2.5. SR03

Character Font
I/O (and Memory Offset) Address: 3C5h (index=03h)
Default: 00h
Attributes: Read/Write
7 6 5 4 3 2 1 0
Reserved (00) Char Map
A Select
(bit 0)
Char Map
B Select
(bit 0)
Character Map A Select
(bits 2 and 1)
Character Map B Select
(bits 2 and 1)
Bit Descriptions
7:6 Reserved. Read as 0s.
3:2,5 Character Map Select Bits for Character Map B. These three bits are used to select the character
map (character generator tables) to be used as the secondary character set (font). Note that the
numbering of the maps is not sequential.
Bit [3:2, 5] Map Number Table Location
00,0 0 1st 8KB of plane 2 at offset 0 (default)
00,1 4 2nd 8KB of plane 2 at offset 8K
01,0 1 3rd 8KB of plane 2 at offset 16K
01,1 5 4th 8KB of plane 2 at offset 24K
10,0 2 5th 8KB of plane 2 at offset 32K
10,1 6 6th 8KB of plane 2 at offset 40K
11,0 3 7th 8KB of plane 2 at offset 48K
11,1 7 8th 8KB of plane 2 at offset 56K
1:0,4 Character Map Select Bits for Character Map A. These three bits are used to select the character
map (character generator tables) to be used as the primary character set (font). Note that the
numbering of the maps is not sequential.
Bit [1:0,4] Map Number Table Location
0,00 0 1st 8KB of plane 2 at offset 0 (default)
0,01 4 2nd 8KB of plane 2 at offset 8K
0,10 1 3rd 8KB of plane 2 at offset 16K
0,11 5 4th 8KB of plane 2 at offset 24K
1,00 2 5th 8KB of plane 2 at offset 32K
1,01 6 6th 8KB of plane 2 at offset 40K
1,10 3 7th 8KB of plane 2 at offset 48K
1,11 7 8th 8KB of plane 2 at offset 56K
NOTES:
1. In text modes, bit 3 of the video data’s attribute byte normally controls the foreground intensity. This bit may be
redefined to control switching between character sets. This latter function is enabled whenever there is a
difference in the values of the Character Font Select A and the Character Font Select B bits. If the two values
are the same, the character select function is disabled and attribute bit 3 controls the foreground intensity.
2. Bit 1 of the Memory Mode Register (SR04) must be set to 1 for the character font select function of this register
to be active. Otherwise, only character maps 0 and 4 are available.