RE: Weird problem writing buffer 1 of a 8250 drive
Date: 2008-09-04 15:51:58

Hallo allemaal,

I already mentioned a work-around:


 100 open1,8,15
 110 open2,8,2,"#1"
 120 print#1,"b-p";2;0
 200 for i=0 to 15 : print i;
 210 print#2,chr$(i); : next
 240 print : print
 400 for i=0 to 15
 410 print#1,"m-r" chr$(i) chr$(18)
 420 get#1,a$ : if a$="" then a$=chr$(0)
 430 print asc(a$); : next
 440 close1 : close2
 0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15

 0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15

This one works as you can see. 

Next (in VICE) I changed line 210 into "print#2,chr$(96); : next" and
added the following lines:

 500 directory
 510 print#1,"m-e" chr$(0) chr$(18)
 520 directory

Line 210 fills the buffer with the value 96 = $60 = RTS. Line 510 will
execute a program starting at address $1200 = Buffer1. Lines 500 and 500
are there to check if the drive is (still) available. Deleting line 510
I see two listings of the directory, with line 510 I only see one :(

I tried the PRG with colon ie. "m-e:" and without the spaces in line 510
but with the same result: drive hangs.

Fortunately I have even a work-around for that problem: 510

 100 open1,8,15
 110 open2,8,2,"#2"
 120 print#1,"b-p";2;0
 200 print#2,chr$(76);
 210 print#2,chr$(183);
 220 print#2,chr$(242);
 240 print : print
 400 for i=0 to 15
 410 print#1,"m-r" chr$(240+i) chr$(255)
 420 get#1,a$ : if a$="" then a$=chr$(0)
 430 print asc(a$); : next
 440 print : print
 500 directory
 510 print#1,"u3"
 520 directory

Looking at the result of lines 400-430 I found out that u3 is associated
with Buffer 2, $1300-$13FF, therefore the use of #2 in line 110. Lines
200-220 insert the command "JMP Reset" into Buffer 2. The results is two
listings plus a delay of several seconds between the actual output to
the screen.

OK. So far we know that m-w and m-e don't work as it should on a 8250.
What I really don't understand that this should be something more people
should have bumped into? I cannot imagine that I'm the first person in
thirty years time encountering this weird problem :)

For those who are interested why I need all this: I want to create a
fast diskcopy program. I created one in the past to copy WordCraft for
Marko but that took ages to copy one disk. The idea I have is a ML that
runs in the memory of the 8250 and transfers the data of every sector
byte for byte to the LPT port of a PC using my own protocol. The
hardware, just a cable, is no problem because I use the one of my CBM-HD

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