80-Bus News


May–June 1984 · Volume 3 · Issue 3

Page 44 of 51

An Improved NAS-SYS?

by Olav Lerflaten

Here are some suggested modifications to NAS-SYS 3. NAS-SYS 3, while an excellent piece of software, has a couple of shortcomings from my point of view. In particular:

– It does not support a parallel printer.
– Access to the ASCII characters “{”, “|”, and “}” is awkward.

The latter point is perhaps of most concern to Scandinavians, as these characters are redefined as special Scandinavian letters. To ease word processing, the requirements are that the small “letters” { | } shall correspond to the capital “letters” [ \ ], respectively, each pair of “letters” assigned to its own key on the keyboard.

Both these shortcomings are corrected by these modifications to NAS-SYS 3. The requirements are:

Nascom 2 keyboard (57 keys)
– Centronics standard printer connector
– PIO port A (8 lines) to printer DATA lines
– PIO line B0 to printer STROBE line
– PIO line B2 to printer BUSY line
– PIO connector ground to printer LOGIC GROUND

The PIO is initialized during power-up, and reset to the printer requirements; this must be taken into account if the PIO is to be used for other purposes.

One problem with Nascom standard software is differences in supplying LF or not after each CR, this gives problems when using printers. On EPSON printers this is easily fixed, as the CR is not needed, only LF may be used to separate lines. Consequently, this NAS-SYS version converts all CRs to LFs, and ignores all LF codes sent from some software packages. If your printer insists on CRs, it should be possble to convert all CRs to a CR and a LF, still ignoring incoming LFs.

To make room for the extra facilities inside the alloted NAS-SYS space, it was necessary to remove some existing code. I chose to attack the register display routine, shortening it so that now it will only display the contents of the Program Counter. After all, if you have DEBUG, you never use it anyway.

Description of new NAS-SYS facilities

a) Keyboard changes

{ and [ are on the “[\” key
| and \ are on the “CH/LF” key
} and ] are on the “]_” key
@ is now unshifted, repeating
_ is Shift/@

Remarks: The @ key is no longer available as an extra CTRL key (this facility is only needed on Nascom-1 keyboards). CH and LF are not very important control codes, consequently they do not need their own key. CH is still

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