Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!jarthur!petunia!news
From: slobasso@raven.calpoly.edu) (I don't know ;-)
Newsgroups: comp.sys.cbm
Subject: Re: ML help!!!
Message-ID: <27584a47.2324@petunia.CalPoly.EDU>
Date: 2 Dec 90 00:26:47 GMT
References: <1990Nov30.161424.2348@uoft02.utoledo.edu>
Reply-To: slobasso@raven.calpoly.edu.UUCP (I don't know )
Organization: Cal Poly State University -- San Luis Obispo
Lines: 44




In article grx0644@uoft02.utoledo.edu writes:
|I wrote an assembly program for my c128. Its a simple program that writes the
|time on the screen in the upper left hand corner. To be useful, it is started
|by a sys statement and returns basic when finished. It uses the cassette buffer
|as its home. I want to have the C128 to execute this program as part of the
|C128's normal routine so I don't have to keep sending a sys command.  is there
|a way to patch something the normal operating routine that will cause the
|computer to JSR to my routine and then RTS back to what ever it was doing,
|without interupting any basic programs that may be executing at the same time?

The best way to do this is to make a ML program run while other things run
is to link it into an interrrupt. I use the IRQ RAM vector. $0314-0315
When your program is done rather than returning (rts) you just
jmp to where the Vector usually points.
here's a sample that changes the border color of the 40col screen

. 01800  78		SEI        ;these 7 lines set up the interrupt vector
. 01801  A9 0D		LDA #$0D   ;LSB of address
. 01803  8D 14 03	STA $0314
. 01806  A9 18		LDA #$18   ;MSB of address
. 01803  8D 15 03	STA $0315
. 0180B  58		CLI
. 0180C  60		RTS

; note that the program starts at the address used above

. 0180D  CE 20 D0	DEC $D020 ;this is your actual program, it finishes by
. 01810  4C 65 FA	JMP $FA65 ;jumping to FA65 (EA31 for the C64)

this program will run while a basic or ML program is running w/o
interrupting it. Try to have the program as small as possible
since it is executed very often. For instance a clock need only be updated
once every second. I think that the interrupt will get called 60 times
a second.


-- 
---                             | I took a course in speed reading and was
Steve LoBasso                   | able to read War and Peace in twenty minutes.
slobasso@polyslo.CalPoly.EDU    | It's about Russia.
ucbvax!voder!polyslo!slobasso   |                    -- Woody Allen