Tandy 26-3334 Service Manual page 12

FF94:
Timer Most Significant Nibble
FF95:
Timer Least Significant Byte
TIMER: This
is a
12-bit interval timer. When
a
value
is
loaded into
the
MSB, the count
is
automatically begun.
The input clock
is
either
14
MHz or horizontal
sync, as selected
by
TINS
(bit
5
of FF91). As
the count falls through zero, an interrupt
is
generated
(if
enabled), and
the count
is
automatically reloaded,
FF96: Reserved
FF97:
Reserved
FF98:
Video Mode Register
BP
= alphanumeric,
1
= bit plane
BIT
BIT
BIT
BIT
BIT
BIT
BIT
BIT =
BPI
MOCH
H50
LPR2
LPR1
LPRO
LPR2
1
1
1
1
1
= Burst phase inverted
1
= monochrome
(on composite)
1
=
50 Hz
vertical sync
Lines per row (See table below)
Lines
per row (See table below)
Lines
per row (See table
below)
LPR1 LPRO
1
1
1
1
Lines per character row
one
two
three
eight
nine
(reserved)
twelve
(reserved)
(Graphics modes)
(CoCo
1
and CoCo
2
only)
(CoCo
1
and CoCo
2
only)
(CoCo
1
and CoCo
2
only)
FF99;
BIT
BIT
BIT
BIT
Video Resolution Register
= LPF1
= LPFO
= HRES2
BIT
3
=
HRES1
BIT
2
=
HRESO
BIT
1
=
CRES1
BIT
=
CRESO
Lines per field (See table below)
Lines
per field
Horizontal resolution
(See
Video resolution
on page
17)
Horizontal resolution
Horizontal resolution
Color resolution
(See Video resolution)
Color resolution
LPFI LPFO
Lines per field
1
1
1
1
192
200
Reserved
225
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