
15-36
Flat Panel Registers
`efmp69030 Databook
Revision 1.3 11/24/99
FR40
Horizontal Compensation Register
read/write at I/O address 3D1h with index at I/O address 3D0h set to 40h
shadowed only for pipeline A
Note: This register is used in FP mode (FR01 Bit 1 set to 1)
7-6
Reserved (R/W)
5
FP Enable Graphics Horizontal Compensation (EGHC)
0: Disable graphics mode horizontal compensation.
1: Enable graphics mode horizontal compensation which consists of horizontal stretching
and FR41 is used to specify stretching for different horizontal resolutions.
This bit is effective only when bit 0 is 1.
4-3
Text Horizontal Compensation Priority (THCP)
These bits are effective only when bit 0 is 1 and bit 2 is 1. These bits determine the text
mode compression/stretching method to be applied if horizontal panel size is wide enough.
If after applying the specified text compression/stretching, the horizontal panel size is still
wider than the stretched image then further stretching will be applied using the same
algorithm used for horizontal graphics compensation.
76543
210
A
Reserved
(00)
EGHC
(0)
THCP
(0:0)
ETHC
(0)
EHC
(0)
EHCP
(0)
B
not shadowed for this pipeline
Bits
4 3
Text Horizontal Compensation Priority (THCP)
0 0
Allow 9-dot compression to 8-dot if needed. If horizontal panel
size is wide enough, 8-dot text remains 8-dot text and 9-dot
text remains 9-dot text. If horizontal panel size is not wide
enough, then 8-dot text remains 8-dot text and 9-dot text is
forced to 8-dot text. This is the default after reset.
0 1
No compression or expansion. 8-dot text remains 8-dot text
and 9-dot text remains as 9-dot text regardless of horizontal
panel size.
1 0
Allow 8-dot expansion to 9-dot, or 9-dot compression to 8-dot,
depending on horizontal panel size. If horizontal panel size is
wide enough, 8-dot text is forced to 9-dot text and 9-dot text
remains 9-dot text. If horizontal panel size is not wide enough
then 8-dot text remains 8-dot text and 9-dot text is forced to 8-
dot text.
1 1
Allow 8-dot and 9-dot expansion to 10-dot, or 8-dot expansion
to 9-dot, or 9-dot compression to 8-dot, depending on
horizontal panel size. If horizontal panel size is wide enough,
8-dot text is forced to 10-dot text and 9-dot text is forced to 10-
dot text. Otherwise, if horizontal panel size is wide enough,
8-dot text is forced to 9-dot text and 9-dot text remains 9-dot
text. If horizontal panel size is not wide enough, then 8-dot
text remains 8-dot text and 9-dot text is forced to 8-dot text.