Appendix C/ Downloading Special Drivers; Downloading Procedure; Program File Format - Radio Shack TRS-80 Operation Manual

Appendix
C/
Downloading
Special
Drivers
The
DOWNLOAD
feature
lets
you
take
full
advantage of your
printer's capabilities by
making
it
possible
to
program
functions
for specialized applications
into the
PTC-64.
For
instance,
you can program
high
resolution graphics support or
special fonts.
Any
program
sent
to the Printer Controller,
however, must
be
in
TRSDOS
load
file
format. This appendix
describes
the
downloading procedure and
the required
format and
structure of
program
files.
Downloading Procedure
To
download
your
drivers
you must
follow
this
procedure:
1.
Send
the
DOWNLOAD
Sequence
(27 38
Dec).
2.
Send
the data
in
TRSDOS
load
file
format (more
on
this later).
You
should
be aware
that
Radio Shack computers do
not send
all
data
to
the printer
directly.
Some
characters
such
as
TABs
and
NULLs
are
intercepted and
not
sent.
Therefore,
a special routine
must be
written
to
send your
data
to
the printer port.
For Models
I, III,
and
4,
you
may
send
data
to
the port
in
BASIC
via the
OUT
or
POKE
command,
depending on
which computer you
are using.
Refer
to the table
below.
For Models
II,
12,
and
16,
you
will
have
to
create an assembly language
routine to send
the
data
to the port.
For more
information on
the printer port,
you
should
refer
to the
Technical Information
section of
the
owner's
manual
for the
computer you
intend
to use.
Computer
Command
Address
Model
I
POKE
14312
(Dec.)
37E8
(Hex.)
Models
II,
12,
16
OUT
225
(Dec.)
El
(Hex.)
Models
II,
4
OUT
248
(Dec.)
F8
(Hex.)
Remember
that
even though you
are
only downloading program
data,
you must
still
monitor
the
BUSY
signal
at the
computer. See
the table
below
for Status port address:
Computer
Command
Address
Bit
Model
I
PEEK
14312
(Dec.) 7
Models
II,
12,
16
IN
224
(Dec.)
7
Models
III,
4
IN 248
(Dec.)
7
Important
Note:
You may
abort
downloading
at
any time (between sending
the
first
and
last
byte of
data)
by
pressing the
CLEAR
key on
the
PTC-64
panel.
This
will print the
following
message
to the
printer:
CLEAR
Rev
pressed* resuming monitor.
Program
File
Format
Programs
sent
to
the
PTC-64
are
composed
of
several blocks.
There
are three major
types
of
blocks:
1.
Program
data
blocks.
These
contain
the actual
program
data, prefixed by four bytes
of header
information.
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