One or two corrections need to be made to previous articles.
Firstly the parallel
printer driver from BASIC,
section 3.2 of
the April newsletter. In
the final value is shown as
217, when it should be 201. This error originated in
Application Note AN-0006, and was due to an error in converting
hex to decimal (I should have used the computer!). The error is
also present in the current BASIC manual. In the
the listing seems to have got slightly corrupted at line number
5 – there should be a line
PORTA EQU 4
to declare the A port address – this seems to have become merged
with a preceding comment line.
Secondly the keyboard interrupt listing in the
I merged this into the SPEX word processor file without looking
properly at the line length. You may therefore find the layout
has been right justified on some long lines, producing an odd
appearance, depending on how the Editor formatted the pages when
producing copies for the newsletter. This should still be
understandable, but is a function of how the text was formatted
rather than being a fault in NAS-SEMBLER.
5. USEFUL INFORMATION
Some users have asked about the access times of different
versions of the Nascom disc drives and the values used in NAS-DOS.
The earler Nascom drives had a 30 mS access time, while the
latest half height units have 6 mS access time. The different
versions can be recognised as follows, listed in chronological
Earliest drives, all plastic sides (no inset metal plate).
Small horizontally mounted pot in the centre of the PCB mounted
on the drive. These are 30 mS drives, but many can be made to
run at 20 mS, although you may need to tweak the pot.
As above, but no pot fitted. These will usually only run
30 mS drives.
Small metal plates mounted on each side of the drive which
carry the mounting screw. These ae 20 mS drives.
Half height drives. These have a 6 mS access time.
The access time is controlled by outputting a byte at one point
– NAS-DOS. This byte is interpreted as follows: