VT8601 Via, VT8601 Datasheet - Page 77

• Manufacturer Part Number: VT8601
• Description: Slot-1 / Socket-370 PCI North Bridge
• Manufacturer: Via

VGA Sequencer Registers (SR)
Port 3C4 – VGA Sequencer Index ................................... RW
Port 3C5 Index 0 – Sequencer Reset ................................ RW
Port 3C5 Index 1 – Sequencer Clocking Mode ............... RW
Port 3C5 Index 2 – Sequencer Map Mask ...................... RW
Port 3C5 Index 3 – Sequencer Character Map Select .... RW
Port 3C5 Index 4 – Sequencer Memory Mode ................ RW
Revision 1.3 September 8, 1999
7-0
7-2
7-6
7-4
7-6
3-2
1-0
7-4
1
0
5
4
3
2
1
0
3
2
1
0
5
4
3
2
1
0
7HFKQRORJLHV ,QF
Sequencer Index
Only the lower 3 bits are implemented in a standard
VGA to point to Sequencer registers 0-4. However,
all 8 bits are implemented here to allow for extended
registers up to index FF.
Reserved
Synchronous Reset
Asynchronous Reset
Reserved
Screen Off
Shift 4
Dot Clock
Shift Load
Reserved
8/9 Dot Clocks
Reserved
Enable Map 3
Enable Map 2
Enable Map 1
Enable Map 0
Reserved
Character Map Select A
Character Map Select B
Character Map Select A
Character Map Select B
Reserved
Chain 4
Odd / Even
Extended Memory
Reserved
:H &
:H &R R QQHFW
QQHFW
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
-71
VGA RAMDAC Registers
Port 3C6 – VGA RAMDAC Pixel Mask ......................... RW
Port 3C6 – VGA RAMDAC Command .......................... RW
This register is a non-standard VGA register (“extension
register”) located at the same port address as the VGA
RAMDAC Pixel Mask register.
compatibility with standard VGA operations, access to this
register is restricted: access is enabled by performing four
successive accesses to the Pixel Mask register at 3C6 (i.e.,
read 3C6 four times).
Port 3C7 – VGA RAMDAC Read Index ........................ WO
Port 3C8 – VGA RAMDAC Write Index ....................... WO
Port 3C8 – VGA RAMDAC Index Readback ................. RO
Port 3C9 Index 0-FF – RAMDAC Color Palette ........... RW
There are 768 data entries in the palette consisting of 256
three-byte entries. R, G, and B 8-bit values are accessed on
successive
autoincremented after every 3 accesses.
programmers guide for further information.
7-0
7-4
7-0
7-0
3
2
1
0
Palette Address Mask
Color Mode Select
Reserved
DAC Disable
Reserved
RAMDAC Enable
RAMDAC Index
RAMDAC Color Data
0000 Pseudo-Color Mode............................... default
0001 Hi-Color Mode (15-bit direct interface)
0010 Muxed Pseudo-Color Mode (16-bit pixel bus)
0011 XGA Color Mode (16-bit direct interface)
01xx -reserved-
10xx -reserved-
1100 -reserved-
1101 True Color Mode (24-bit direct interface)
111x -reserved-
0
1
0
1
operations
DAC On (if SR20[0] = 1) ...................... default
DAC Off
Disable (Bypass) RAMDAC.................. default
Enable RAMDAC
........................................always reads 0
........................................always reads 0
VT8601 Apollo ProMedia
to
this
port
In order to maintain
with
Refer to a VGA
VGA Registers
the
index