Radio Shack 26-1145 - Page 33

Assuming the
specific
interface
requirements
are identical
to
this
example,
now all you
do
is type in the
BASIC program
listed on
page
28,
run
it
and
now you are ready
to use a
serial
line
printer
with
BASIC. A
step-by-step
illustration
of this
procedure is shown
below.
1
.
Power
up TRS-80
and Expansion
Interface.
MEMORY
SIZE?
should
be displayed
on the Video
Monitor.
You should
respond with:
32511
and press
I3'ii3;l
(Decimal
equivalent
of 7EFFH).
This
response
reserves the
top
256 bytes of a 16K TRS-80
for the printer driver.
2. Set
configuration
switches
for
desired baud rate,
stop
bits,
word length
and parity
as
required.
See esample
on page x.
3. Type in the
BASIC
program
listed
on page xx with
appro-
priate modifications
for
specific
application
or load from
cassette
a previously
saved version
of the above.
4.
Run
the BASIC
program.
5. Connect
the Line Printer
to the RS-232-C
with
the cable
provided
(or an
appropriately
modified
cable).
6. Now
you can
use
a
serial
line printer
with the
Level II
BASIC
LPRINT
and
LLIST commands.
Any BASIC
programs which
utilize
this
technique
must include
the
BASIC
program on page
29
as a
part of the coding
and
this
section of
code
must
be executed
prior
to using
the
serial line
printer. If you
do not want
to locate
the
object code for
the
line
printer driver
at
7F00H (as in this
example),
you can reassemble
the source
code on
page
27
with a different
origin
(line
140)
using
the TRS-80
Editor
Assembler
and modify
the BASIC
program
to
correspond
to this
new
location.
The response
to the
memory
size question
must
also be
modified to be the decimal
equivalent
of
one
byte less than
the
beginning
address of the line
printer
driver
object
code. The
data
statements in
the BASIC
program
on page xx must
be
altered
to
reflect any change
in the
object
code due
to relocation
or modifica-
tion. The
last two poke statements
on line
20 on page 28 must
be
changed
to correspond
to the
decimal
equivalent
of the new
beginning
address of the driver
object
code (argument
of second
poke statement
is the low-order
byte of the new
address,
and the
argument
of the
third poke statement
is the high-order
byte of the
new
address).
30