[Coco] CoCoNet bug in BASIC
operator at coco3.com
Mon Nov 30 01:22:11 EST 2009
I need help here guys... put your thinking caps on so the CoCoNet
client ROM can be released sooner?
This is getting crazy. For two weeks I've seen the bug come and
go. I've looked at the BASIC source code (Unravelled Series) and
can't figure out why it's happening or what I'm doing to make it happen.
Only when the Drive Pak is accessed (the MicroSD card is read or
written to) does this seem to happen. Yet, when I issue the command
DRIVE#? to see a listing of the partitions, the bug goes away until
the next time I type DIR or load a program, etc. Both commands
access the pak, but DRIVE#? uses the raw sector reader, bypassing the
track/sector computer to get the LSN offsets. It jumps over that
part and uses registers A and X for the 24-bit LSN and uses the SAME
sector read/write routines to do the transfer.
What's happening is that when you go to EDIT or insert a BASIC
program line, the line and following lines of the program VANISH from
the listing. Peeking into memory shows that NULL bytes were
inserted, as if the program was opened up for the insertion, but
nothing was inserted! The space is there, though.
This has caused me a Lot of lost sleep and is the reason the CoCoNet
ROM hasn't been released yet. Other than that, the Drive Pak is
functioning like it should at 230400 bps, boots into DOS or OS-9 in
any partition you like. The Wirless Pak, bitbanger drives, etc.
don't cause the bug to happen.
I feel that this is related to me switching to the ROM map
temporarily to access routines in the upper 8K of the 16K CoCoNet
ROM. I always mask interrupts and restore after I've returned back to
the bottom 8K of my ROM.
The CoCo 3 patch guys really gave us a nightmare once you have to
work with the ROMs more in a project like this. They butchered the
crap out of BASIC and did things that make little sense. They were
under pressure and just got it done, apparently. They made it work
and left bugs and made it hard to use a 16K DOS, that's for sure.
So, what on Earth is in the BASIC code that would open up an area in
a BASIC program in prep for the insertion of a new line or the
replacement of an edited line, but doesn't actually insert those
characters? What would be stopping the second action from
happening? The input buffer looks empty or returns NULL characters
perhaps? A corrupt pointer? I don't mess with any of that, so
what's the problem?
Btw, the partitioning commands have been added to Disk BASIC and more
to be added tomorrow... you can list the partitions, set the
auto-boot partition by name or direct LSN, and set the current
temporary DOS partition (256 drives)... which gets overridden by the
auto-boot partition the next time you boot.
DRIVE# is the prefix for the MicroDrive (Drive Pak) commands.
DRIVE#="MYDISKS",DOS make pak boot to the MYDISKS partition of 256
disks on each boot, and sets the current partition to the same
DRIVE#="MYGAMES" change to partition temporarily until changed again
DRIVE#=#0,0,0 point to LSN-based area of 256 disks (for surgery mode)
DRIVE#=#0,0,0,DOS auto-boot to any LSN (treated as 256 virtual disks
like the above partitions) (unusual need to do this, but it's there)
*.BAS is the auto-boot program looked for on DRIVE 0 of any auto-boot
DRIVE#+"MYGAMES" add a partition (size and starting LSN optional)
(180mb is the default size so OS-9 can use 720K disks without worries)
DRIVE# KILL "DATALOG" remove 256 disks partition called "DATALOG" (180mb)
DRIVE# SET 0,0,1 (the default already) set partition table to LSN1
(shouldn't be changed once partitions are added to the table)
DRIVE#? list partitions (name, starting LSN, size, type) The Type
doesn't really matter
DRIVE show currently mounted disks (wireless, real, bitbanger,
drive pak, ram disk, etc.)
I might have left some stuff out here, but you get the idea.
The defaults are LSN0 system use, LSN1 partition table start, LSN
$002000 'DOSFD0' 256 disks, and NitrOS-9 is 180mb past that, with 782
megs to go on my 2gb card.
Until partition moving and advanced logic is added when
deleting/inserting partitions, it's better to start with a clear
partition table and add the partitions in sequence. If the power
goes out when you're working with the partition table entries, the
data isn't lost, btw. In tests and goofups, I've repeatedly cleared
my table and gone back and inserted the standard partitions in
sequence and got my drive pak restored, all data intact.
It's pretty fun doing this from the command prompt, but I've got a
PART.BAS program that attempts to simplify the adding of partitions,
showing you the types, sizes in MB, starting LSN, etc. all computed
~ Roger Taylor
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