Radio Shack TRS-80 Model III - Page 90

TRS-80
MODEL
III
(BREAK)
Processing
The
(BREAK)
key is
intercepted
during
keyboard
scan
operations.
The
Computer
transfers
control to
a three-byte
jump vector
in RAM
(hex values:
C3 Isb
msb). For
special
applications,
you
may change
the
jump
vector addresses
to
allow
your own
program
to
handle the
(BREAK)
key
.
Thekeyscan
(BREAK)
jump
vectoris
located
at
16396 (X'400C)-
Register
contents
on entry
to the
jump vector
DE
=
Modified
by the
Computer
(SP)
=
The
return
address of
the
interrupted
program.
That
is,
a
RET
will
transfer
control
to the
point
at
which the
program
was interrupted.
Sample
BASIC
Programming
Run this
BASIC
program
to disable
(BREAK)
.
10
POKE
16396,175
>
1
75
=
Z-80
" XOR A" CODF
20
POKE
16397,201
'201
==
Z-80
"RET" CODE
Run
this
BASIC
program
to enable
the
(BREAK)
key.
10
POKE
16396,201
'Z-80 "RET"
CODE
80