Appendix
B/
Model
4/4P
Hardware
The Keyboard Code
Map
The keyboard code map shows the code that TRSDOS returns for
each key,
in
each of the modes: control, shift, unshift, clear and
control, clear and shift, clear and unshift.
For example, pressing
(CLEAR),
(SHIFT),
and
CD
at
the same time
returns the code
X'
A1
'.
A program executing under TRSDOS - for example, BASIC - may
translate some of these codes into other values. Consult the
program's documentation for details.
(BREAK)
Key Handling
The
(BREAK)
key (X'80')
is
handled
in
different ways, depending
on
the
settings of three system functions. The table below shows what
happens for each combination of settings.
Break Break Type-
Enabled Vector Ahead
Set Enabled
y
N Y
If
characters are
in
the type-
ahead buffer, then the buffer is
emptied.
*
If
the type-ahead buffer is
empty, then a BREAK character
(X'80') is placed
in
the
buffer.
*
y
N N A BREAK character (X'80') is
placed
in
the buffer.
y y y
The type-ahead buffer
is
emptied
of its contents (if any), and
control is transferred to the
address
in
the BREAK vector
(see
@BREAK SVC).
*
y y
N Control
is
transferred to the
address
in
the BREAK vector
(see
@BREAK SVC).
N X X
No
action
is
taken and
characters
in
the type-ahead
buffer are not affected.
y
means that the function is on or enabled
N means that the function is off or disabled
X means that the state of the function has no effect
~.
A-35
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