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Tandy 1000 Technical Reference Manual

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Tandy
1000
8255A18255A·5
Input Control Signal Definition
Technical Reference Manual
STS
(Strobe
Input).
A
"low"
on
this
input
loads
data
into
the
input
latch.
IBF (Input Buffer Full F/F)
A
"high"
on
this
output
indicates
that
the data
has
been
loaded
into
the
input
latch; in essence,
an
acknowledgement
ISF
is
set
by
STB
input
being
low
and
is
reset
by
the rising
edge
of
the
RD
input.
INTR (Interrupt Request)
A
"high"
on
this
output
can
be
used
to
interrupt
the CPU
when
an
input
device
is
requesting service.
INTR
is
set by
the STB
is
a
"one",
IBF
is
a
"one"
and
INTE
is
a
"one".
It
is
reset by the
falling
edge
of
RD.
This procedure
allows
an
input
device
to
request service
from
the CPU
by
simply
strobing
its
data
into
the
port.
INTE
A
Controlled
by
bit
set/reset
of
PC
4
INTE B
Controlled
by
bit
set/reset
of
PC2.
2
PCb)
----/--
I/O
---_c
Figure
8.
MODE 1 Input
_________
--+--J/~
STS
!~
________
..J
I S
IT
~
...
I
\!
-~~.---
\"""---,.....-.------'1'-
~~~~:HFE~~~
- - -
-{'----------tl-~>-
-------------------
--
Figure
9.
MODE 1 (Strobed Input)
6-174

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Tandy 1000 Specifications

General IconGeneral
ProcessorIntel 8088
Processor Speed4.77 MHz
RAM128 KB (expandable to 640 KB)
Operating SystemMS-DOS 2.11
ManufacturerTandy Corporation
Release Year1984
StorageSingle or double 5.25" floppy disk drive (360 KB), optional hard drive
SoundTandy 3-voice sound
PortsParallel, Serial
GraphicsCGA (Color Graphics Adapter)
Graphics Modes320x200, 640x200

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