Radio Shack TRS-80 Model II Reference Manual page 189

Technical Information
Contents ofB Result
B
=
0
Tum off
(HOLD)
processor. Pressing
(HOLD)
will generate
keyboard data X'QQ'.
B
=
1 Tum on (HOLD) processor. Pressing (HOLD) will not generate keyboard
data; it will be intercepted by TRSDOS.
B> 1 Check for (HOLD) key. If it has been pressed one or more times,
pause until it is pressed again. No matter how many times
(HOLD)
is
pressed before this function is called, it will be interpreted as a
single keystroke, thus starting the pause.
Exit Conditions
NZ
(HOLD)
processor is off.
User Notes
To use this function, first tum on the
(HOLD)
processor by calling the SYC with
B
=
1. Then, when you want to check whether (HOLD) has been pressed, call it again
with B> 1.
If(HOLD)
has been pressed, the routine will not return until
(HOLD)
is
pressed a second time.
Returning to the TRSDOS READY command level turns off the
(HOLD)
processor.
However, you can execute a command without turning off the
(HOLD)
processor.
See SYC's JP2DOS and DOSCMD. Some commands like DIR, LIST, etc., will reset
the
(HOLD)
processor.
JP2DOS
Jump to DOS (function 36)
This program simply returns control to the command level (TRSDOS READY).
All Open files are Closed automatically.
Entry Conditions
A
=
36
Note: An alternate way to perform this function is to execute an RST0 instruction.
There are no entry conditions for this method.
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