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ncr.txt
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1993-01-22
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312 lines
NCR 77C22E VGA
NCR 77C21
NCR 77C22
NCR 77C22E 4MB, 1280x1024 256 col
NCR 77C22E+
3C4h index 5 (R/W): Extended Function Enable Register
bit 0 Enables extended registers if set.
1 Reserved (always 0).
2 If set the Hardware Configuration registers (3C4h index 23h bit 0-3,
index 27h bit 1, index 1Fh bit 5 and index 1Eh bits 0-1) can be
modified.
3-7 Reserved
3C4h index 8 (R): Version Number Register
bit 0-3 Chip revision
4-7 Product Code: 0=77C22, 1=77C21, 2=77C22E and >=8 is 77C22E+.
3C4h index 0Ah (R/W): Cursor Foreground Color Register
bit 0-7 Foreground color of the Bit Mapped Cursor.
Plane 0=0 and plane 1=1.
3C4h index 0Bh (R/W): Cursor Background Color Register
bit 0-7 Background color of the Bit Mapped Cursor.
Plane 0=0 and plane 1=0.
3C4h index 0Ch (R/W): Cursor Control Register
bit 0 Cursor enable. When set enables the Bit Mapped cursor.
1-2 Cursor height select.
0=16 lines, 1=32 lines, 2=64 lines and 3=128 lines.
3 Blink frequency select. If set the Bit Mapped Cursor is on for 16 frames
and off for another 16 frames. If clear it is on for 8 frames and off
for another 8 frames.
4 If set the Bit Mapped Cursor blinks.
5-7 Reserved.
3C4h index 0Dh (R/W): Cursor X Location High register
bit 0-2 Bits 8-10 of the horizontal position of the Bitmapped Cursor.
The lower 8 bits are in 3C4h index 0Eh.
3-7 Reserved
3C4h index 0Eh (R/W): Cursor X Location Low register
bit 0-7 Lower 8 bits of the horizontal position of the Bitmapped Cursor.
The upper 3 bits are in 3C4h index 0Dh.
3C4h index 0Fh (R/W): Cursor Y Location High register
bit 0-1 Bits 8-9 of the vertical position of the Bitmapped Cursor.
The lower 8 bits are in 3C4h index 10h.
2-7 Reserved
3C4h index 10h (R/W): Cursor Y Location Low register
bit 0-7 Lower 8 bits of the vertical position of the Bitmapped Cursor.
The upper 2 bits are in 3C4h index 0Fh.
3C4h index 11h (R/W): Cursor X Index Register.
bit 0-5 Horizontal location of the Hot Spot from the left of the cursor.
6-7 Reserved.
3C4h index 12h (R/W): Cursor Y Index Register.
bit 0-4 Vertrical location of the Hot Spot from the top of the cursor.
5-7 Reserved.
3C4h index 13h (R/W): Cursor Storage Register High.
bit 0-7 Bits 8-15 of the address of the cursor bitmnap.
The lower 8 bits are in 3C4h index 14h.
3C4h index 14h (R/W): Cursor Storage Register Low.
bit 0-7 Bits 0-7 of the address of the cursor bitmap.
The upper 8 bits are in 3C4h index 13h.
3C4h index 15h (R/W): Cursor Storage Offset Register High.
bit 0-7 Bits 8-15 of the Cursor Storage Offset.
The lower 8 bits are in 3C4h index 16h.
3C4h index 16h (R/W): Cursor Storage Offset Register Low.
bit 0-7 Bits 0-7 of the Cursor Storage Offset.
The upper 8 bits are in 3C4h index 15h.
If extended memory is enabled (3C4h index 1Eh bit4 set)
the Cursor Storage Offset is multiplied with 16 and added
to the Cursor Storage Address to form a 20 bit address.
3C4h index 17h (R/W): Cursor Pixel Mask Register.
bit 0-7 Each bit set allows the corresponding bit in a pixel to be
affected by the Bitmapped Cursor.
3C4h index 18h (R/W): Primary Host Offset Register High.
bit 0-7 Bits 8-15 of the Primary Host Offset.
The lower 8 bits are in 3C4h index 19h.
3C4h index 19h (R/W): Primary Host Offset Register Low.
bit 0-7 Bits 0-7 of the Primary Host Offset.
The upper 8 bits are in 3C4h index 18h.
If extended memory is enabled (3C4h index 1Eh bit4 is set)
all Host addresses are modified by multiplying either the
Primary or the Secondary Host Offset with 16 and adding
the result to the Host address.
If 3C4h index 1Eh bit is set all read operations use the
Secondary Host Offset and all write opeartions use the
Primary Host address, otherwise both read and write operations
use the Primary Host Offset.
3C4h index 1Ah (R/W): Display Offset Register High.
bit 0-7 Bits 8-15 of the Display Offset.
The lower 8 bits are in 3C4h index 1Bh.
3C4h index 1Bh (R/W): Display Offset Register Low.
bit 0-7 Bits 0-7 of the Display Offset.
The upper 8 bits are in 3C4h index 1Ah.
If extended memory and Display Offset are enabled (3C4h
index 1Eh bit4 and 3 are both set) the Display Offset
is multiplied with 16 and added to the normal display address.
3C4h index 1Ch (R/W): Secondary Host Offset Register High.
bit 0-7 Bits 8-15 of the Secondary Host Offset.
The lower 8 bits are in 3C4h index 1Dh.
3C4h index 1Dh (R/W): Secondary Host Offset Register Low.
bit 0-7 Bits 0-7 of the Secondary Host Offset.
The upper 8 bits are in 3C4h index 1Ch.
If extended memory and Secondary Offset are enabled (3C4h
index 1Eh bit4 and 2 are both set) all read operations
are modified by multiplying the Secondary Offset by 16
and adding the result to the Host address.
3C4h index 1Eh (R/W): Extended Memory Enable Register.
bit 0-1 DRAM configuration. These bits can only be modified
if 3C4h index 5 bit 2 is set.
2 If this bit and bit 4 are set all read operations are
modified by multiplying the Secondary Host Offset by 16
and adding the result to the host address.
3 If this bit and bit 4 are set all display addresses are
modified by multiplying the Display Offset by 16
and adding the result to the normal display address.
4 If set extended memory is enabled.
5-7 Reserved.
3C4h index 1Fh (R/W): Extended Clocking Mode.
bit 0-3 If bit 4 set this determines the font width:
0 4 bit wide font
1 7 bit wide font
2 8 bit wide font
3 9 bit wide font
4 10 bit wide font
5 11 bit wide font
6 12 bit wide font
7 13 bit wide font
8 14 bit wide font
9 15 bit wide font
0Bh 16 bit wide font
4 If set enables extended font width.
5 Clock Output enable.
6 Clock Select Bit 2
7 Reserved
3C4h index 20h (R/W): Extended Video Memory Addressing Register
bit 0 Addition of host address bit 16.
1 Extended chain-4 enable.
2-7 Reserved.
3C4h index 21h (R/W): Extended Pixel Control Register
bit 0 Enable graphics byte path if set.
1 Enable packed/nibble pixel format (2 pixels of 4 bits per byte) if set.
2-7 Reserved.
3C4h index 22h (R/W): Bus Width Feed Back Register.
bit 0 Enables 16 bit memory access if set.
1 Enables 16 bit I/O access if set.
2-7 Reserved.
3C4h index 23h (R/W): Performance Select Register
bit 0 Reserved (Burst Enable).
1 Selects 3 clock RAS cycles if set. Should not be set!!
2 Enables Fast Page Mode if set. Set by external resistor.
3-5 Reserved.
6 Unlatched Memory Writes (Only in 256 color modes with OSC3).
If set limits the duration of CHRDY assertion time by limiting FIFO
fill lengths.
7 Latched Memory Reads. If set the assertion of CHRDY can be
eliminated during read cycles.
3C4h index 24h (R/W): Color Expanded Write Foreground Register.
bit 0-7 When in expanded write mode (3C4h index 26h bit 0 set)
a monochrome bitmap can be expanded to 256 or 16 colors
8 or 16 pixels at a time. '1' bits in the bitmap are expanded
to this color. For 16 color modes only bit 0-3 are used.
3C4h index 25h (R/W): Color Expanded Write Background Register.
bit 0-7 When in expanded write mode (3C4h index 26h bit 0 set)
a monochrome bitmap can be expanded to 256 or 16 colors
8 or 16 pixels at a time. '0' bits in the bitmap are expanded
to this color. For 16 color modes only bit 0-3 are used.
3C4h index 26h (R/W): Extended Read/Write Control Register.
bit 0 FG/BG Color Expansion Enable.
When set enables expansion from monochrome bitmaps to
full color using 3C4h index 24h and 25h as fore- and background
col