6845 Crt Controller; Initial Chip Values - HP Vectra Reference Manual
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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
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