HP Vectra - Page 113

Light Pen
Any access to I/O address 3DB, read or write, will clear the light
pen latch. No data
is transferred, if a read is performed the data
returned
is meaningless.
Any
access to I/O address 3DC, read or write, will set the light pen
latch. No data
is transferred, if a read is performed, the data
returned
is meaningless.
Extension Control Register
The extension control register is a 6-bit write-only register.
The programmer
has control over the font style, but not the
height. The type of monitor determines the cell size of the
alphanumeric character font.
.~
......
Bit
Data
Definition
0 0
Vertical Resolution, emulate 200 line display
1 Enable
400 line display
0 Underline Enable, normal
1 Enable underline
if bits 2-0 are 001.
2
0
Font Select,
STD on Display Graphics page 1
1
HP, Roman 8 font on Display Graphics page 2
3
0
Memory Disable, normal
1 Disable memory from responding
to RIW access.
4 0 16/32K select, wrap first 16K into 32K
1
Use all 32K
.~
5 0 Page, use first 16K
1
Use second 16K (graphics)
96 Multi-Mode Video Adapter Card