Appendix Bi Model 4/4P Hardware; Keyboard Code Map - Radio Shack TRS-80 Model 4 Owner's Manual

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
~.
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