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Tandy 1000 Technical Reference Manual

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Tandy 1000
inter
Combinations
of
MODE
1
8255A18255A·5
Technical Reierence Manual
Port A and Port B
can
be
individually defined
as
input
or
output
in Mode 1
to
support a wide variety
of
strobed
I/O
applications.
PC",
-.--IBr
A
D
J
Db
D"
\)4
OJ
02
D
1
Do
l
'
liO,'
a
><J
! PC
6
,]
-'=!NPUT
0-
OUTPUT
PC
l
-----OBFs
PURT A
ISTRQBED
INPUTI
PORT
B
(STROBED
OUTPUTl
D]
06
0",
04
OJ
PI
01
00
l' I0
':
a:
',0
1
1)<]
I
PC
4
"J
1--.
1
INPUT
0-
OUTPUT
PORT A
PORTS
2
PC~,5
-/
-
1'0
Operating
Modes
Figure
12.
Combinations
of
MODE 1
Output
Operations
------------
MODE
2
(Strobed
Bidirectional
Bus
110).
This
functional
configuration
provides
a means for
communicating
with
a
peripheral
device or
structure
on a
single
B·bit
bus
tor
both
transmitting
and
receiving
data
(bidirectional
bus
1/0)
"Handshaking"
signals
are
provided
to
maintain
proper
bus
flow
diSCipline in a
similar
manner
to
MODE
1.
Interrupt
generation
and
enable/disable
functions
are
llso
available.
MODE 2
Basic
Functional
Definitions
•
Used
in Group A
only.
• One B-bit. bi-directional bus Port (Port AI
and
a 5-oit
control Port (Port
Cl_
• Both inputs and outputs
are
latched.
• The 5-bit control
port
(Port
CI
is
used
for
control
and
status
for
the B-bit, bi-directionel bus port (Port
A).
Bidirectional
Bus I/O
Control
Signal
Definition
INTR
(Interrupt
Request). A
high
on
this
output
can be
used
to
interrupt
the
CPU
for
both
input
or
output
opera-
tions.
OBF
(Output
Buffer
Ful). The
OBF
output
will
go
"low"
to
indicate
that
the
CPU has
written
data
out
to
port
A.
ACK
(Acknowledge).
A
"low"
on
this
input
enables
the
tri-state
output
buffer
of
port
A
to
send
out
the data.
Otherwise,
the
output
buffer
will
be in the high im·
pedance
state
INTE 1
IThe
INTE
Flip·Flop
Associated
with
OBF). Con-
trolled
by
bit
set/reset
of
PC
6
.
Input
Operations
STB
(Strobe
Input)
STB
(Strobe
Input). A
"low"
on
this
input
loads data
into
the
input
latch
IBF
(Input
Buffer
Full
F/F). A
"high"
on
this
output
in-
dicates
that
data
has been loaded
into
the
input
latch.
INTE 2 (The INTE
Flip.Flop
Associated
with
IBF). Con-
trolled
by
bit
set/reset
of
PC
4
.
6-176
AFN-00744C

Table of Contents

Other manuals for Tandy 1000

Preview: User Guide
User Guide337 pages
Preview: Programmer's Reference Guide
Programmer's Reference Guide251 pages
Preview: Basic Reference Manual
Basic Reference Manual411 pages
Preview: Owner's Manual
Owner's Manual46 pages

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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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