Radio Shack TRS-80 Owner's Manual page 126

r—
~"*sj
25^-;
~*r iT^-j^ijl.
-
—
'^_«^r_ir~iK
^^^^v
^ggi^
DEFUSE
Delne
Point of Entry
for
USM
Routine
s.';
-
address
n equals
osse of tne digits
:
1
.
. .
.
S:
it
«
is
an-itied.
G
is
assumed, address
specifies the erdry address
?c g
machine-language
routine.
address
must
be
in
the
.ange
[
-32768,32767].
addressing
be any numeric
expression
or constant from
-32768
to
32767.
defusr
lets
you
define the entry points
for
up
to
10 machine-language
routines.
In
non-Disk
basic, the addresses were
POKEd
into
ram.
This
poke method
cannot be used
in
Disk
basic.
Examples
DEFUSR3
=
8.H7D00
assigns the entry point X'7D00',
32000
decimal,
to the
USR3
call.
When
your
program
calls
USR3,
control will
branch
to
your
subroutine beginning
at
X'7D00\
DEFUSR
=
(BASE
+ IB)
assigns
start
address
(base
+
16) to
the
usro
routine.
Note:
When
decimal addresses
are
given, they
are
evaluated
as signed two-byte
integers. So,
for
addresses
above 32767,
use desired decimal address
-65536.
See usrh.
INSTR
Search
for Specified String
position specifies
the position
in
string
1
where
the?
search
is
to
begin.
position
is
optional;
iJ ft
ss not supplied, search automatically begins
at
the
first
character
in
string
?.
{Position
1
is
the
first
character
in
stmo
1
108