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FF20
-
FF23
PIA
IC4
FF20:
BIT
=
CASSETTE DATA INPUT
BIT
1
=
RS-232C DATA OUTPUT
BIT
2
= 6
BIT D/A LSB
BIT
3
= 6
BIT D/A
BIT
4
=
6
BIT D/A
BIT
5
=
6
BIT D/A
BIT
6
=
6
BIT D/A
BIT
7
=
6
BIT D/A MSB
FF21;
BIT
BIT
1
BIT
BIT
BIT
BIT
BIT
BIT
FF22:
fO
=
FIRQ*
to
CPU Disabled
\l
=
FIRQ*
to
CPU Enabled
fO = sets flag on
falling edge CD
U
=
Control
of the CD
(RS-232C status)
Interrupt
Control
of
Interrupt
Polarity
(^1
= sets flag on
rising edge CD
Normally
1:0=
changes FF20
to the
data direction register
Cassette Motor Control:
=
OFF
1
=
ON
1
Always
1
Always
Not Used
CD Interrupt Flag
BIT
=
RS-232C DATA INPUT
BIT
1
=
SINGLE BIT SOUND OUTPUT
BIT
2
=
RAM SIZE INPUT
BIT
3 =
RGB Monitor Sensing INPUT
BIT
4
=
VDG CONTROL OUTPUT
BIT
5
=
VDG CONTROL OUTPUT
BIT
6
=
VDG CONTROL OUTPUT
BIT
7
=
VDG CONTROL OUTPUT
CSS
GMO
&
UP PER/
LOWER CASE*
GM1
&
INVERT
GM2
A*/G
FF23:
=
FIRQ*
to
CPU Disabled
1
=
FIRQ*
to
CPU Enabled
BIT
2
BIT
3
BIT
4
BIT
5
BIT
6
BIT
fO
=
sets flag on
falling
edge
CART*
U
=
BIT
Control of
the
Cartridge
Interrupt
BIT
1
Control of Interrupt
Polarity
^1
=
gets flag on
rising edge CART*
Normally
1:
=
changes FF22
to the
data direction register
Sound Enable
1
Always
1
Always
Not used
7
=
Cartridge Interrupt Flag
FF40
-
FFBF: Not
used
Note: FF22, FF23 are
duplicated
in
tcclOH
(VC2645QC), and V.D.G Control Bit
(Bit
3
through Bit
7)
affects
this IC (TCC1014) only.
-10-
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