The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

esident routine into its execution location in memory. The first thing that must be done
is to move the contents of the @ICNFG vector into your initialization routine. The code:
LD A,@FLAGS$ ;Get flags pointer
RST 40 ; into register IY
LD A,(IY+28) ;Get @ICNFG byte 1
LD (LINK),A ; & save in LINK+0
LD L,(IY+29) ;Get address LOW and HIGH
LD H,(IY+30) ; then save in the
LD (LINK+1),HL ; LINK address vector
does this by transferring the three byte vector to your routine. You then need to
relocate your routine to its execution memory address. Once this is done, transfer the
relocated initialization entry point to the @ICNFG vector as a jump instruction with this
code:
LD HL,INIT ;Get (relocated)
LD (IY+29),L ; init address
LD (IY+30),H
LD A,0C3H ;Set JP instruction
LD (IY+28),A
It is sometimes necessary to have your initialization program execute the initialization
routine so that the function of the module is immediately available. You probably do not
want to execute any other routines that may be chained into @ICNFG so you should not CALL
the chain! Your initialization routine can be executed by calling its relocated address
as in:
CALL ROUTINE ;Initialize only mine
Don't forget to SYSGEN after linking in your routine. The SYSGEN process includes saving
the revisions to @ICNFG so that any changes will be part of the system configuration the
next time the disk is booted. By following these procedures, you can effect the
invocation of your routine every time you boot the operating system disk which contains
this configuration.
8.2 THE KFLAG$ SCANNER
Many applications have the need to detect a PAUSE or BREAK condition while they are in
execution. BASIC does this after every logical statement is executed (i.e. after each end
of line or ":" statement separator). That's how, in BASIC, you can stop a program with
the key or pause a listing. The classical method that programmers have used to
detect the condition was to scan the keyboard via the @KBD SuperVisor Call. If a
character was input, and it was a or a , the appropriate action would be
taken. Any other entry that was available would be ignored which would discard all other
keyboard entries. Unfortunately, if the user was trying to make use of keyboard typeahead,
each @KBD request looking for or would extract one character from
the type-ahead buffer; thus the user's typed-ahead entries would be lost.
Another method could be used on a matrix keyboard that is accessible to the application.
This method does not request entries via the @KBD call but scans the keyboard physically
examining the keyboard matrix. A problem with this method is that accessible matrix
keyboards are not always available. A second problem is that if such a keyboard was
available, the application would not be portable across Version 6 installations.
If an application uses the KFLAG$ keyboard function latch to observe the BREAK or PAUSE
condition, it overcomes these deficiencies [a third condition - that of the ASCII CR is
also supported]. KFLAG$ contains three bits associated with the "keyboard" functions of
BREAK, PAUSE (sometimes interpreted as ), and CR (sometimes interpreted as
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