HP Vectra User Manual

6845 CRT Controller
The 6845 CRT controller (CRTC) contains 19 internal registers. One
of these is the index register. It is accessed at any even I/O address
in the range 3DO-3D6. This write-only register functions as a
pointer
to the other 18 registers in the chip. Reading it will return
an undefined value. The 18 internal data registers are accessible at
any odd I/O address in the range 3D1-3D7, after first setting the
index
to point to it. Table 6.7 defines the initial values that should
be sent to the CRTC chip.
Table 7.7
Initial Chip Values
Mode
6845 Data register
25kHZ
Hz
Note RO R1 R2 R3 R4 R5 R6 R7 R8 R9
R10 R11
308
300
80x25 A 60
**
60 50 57 OA 19 09 19 19 00 OF OE OF 00 00
40x25 A 60
**
36 28 2C OA 19 09 19 19 00 OF DE
OF
DC
00
80x27 A 60 60 50 57 OA 10 05 18 1C 00 00 00
OE
00 00
40x27 A 60 36 28 2C OA 10 05 18 1C 00 00 00 OE
DC
00
320x2x200 60
**
36 28 28 OA 69 01 64 66 00 03 OE OF OE 00
640x1x200 60
**
36 28 28 OA 69 01 64 66 00 03 OE OF 1E 00
320x2x400
60
36 28 28 OA 69 01 64 66 00 03 OE OF OE 11
640x1x400 60 36 28 28 OA 69 01 64 66 00 03
OE OF
1E 11
80x25 A
50
**
6D 50 57 OA 1E OE 19 1C 00 OF OE OF 00
00
40x25 A 50
**
36 28 2C OA 1E OE 19 1C 00 OF
OE
OF OC 00
80x27 A 50
++
60 50 57 OA 23 06 18 1F 00 00 DC 00 00
00
40x27 A 50
++
36 28 2C OA 23 06 18 1F 00 00 OC
00
OC 00
320x2x200 50
**
36 28 28 OA 7E 02 64 70 00 03 OE OF OE 00
640x1x200 50
**
36 28 28 OA 7E 02 64 70 00 03 OE OF
1E
00
320x2x400 50
++
36 28 28 OA 7E 02 64 70 00 03 OE OF OE
11
640x1x400
50
++
36 28 28 OA 7E 02 64 70 00 03
OE
OF
1E
11
15kHZ
80x25 A
60 71
50 SA OA
1F
06
19 1C 02 07 06 07 00
00
40x25 A 60
38 28 20 OA
1F
06
19 1C 02 07 06
07
OC
00
320x2x200 60
38 28
20 OA 7F 06 64 70 02 01 06
07
OE
00
640x1x200
60 38 28 20 OA 7F 06 64 70 02
01
06
07
1E 00
80x25 A 50
71
50 SA OA 26 02 19 1F 02 07 06 07 00 00
40x25 A 50
38 28
20 OA 26 02
19
1F 02 07
06
07
OC
00
320x2x200
55 *
38 28 20 OA
7F 1F 64 75 02 01 06 07 OE 00
640x1x200
55 *
38 28 20 OA
7F 1F 64 75 02 01 06 07
1E
00
*Oue to limitations of the 6845 registers, 50Hz graphics is not possible.
* *These modes should be programmed
with 15KHz 60Hz values. They will be translated
according
to the W1 f\N2 jumper settings on the board.
+ +These modes shoud be programmed with 25KHz 60Hz values. They will be translated
according
to the W1 jumper setting on the board.
90 Multi-Mode Video Adapter Card

HP Vectra Specifications

General

Processor	Intel Pentium
RAM	Up to 128 MB
Storage	HDD (capacity varies by model)
Operating System	Windows 95
Graphics	Integrated
Ports	Serial, Parallel
Expansion Slots	ISA, PCI