Written by CCaoft, NAS-GRAPHPAC links with the standard Nascom ROM BASIC to
provide twenty additional commands for controlling the Nascom 2’s low-resolution
graphics. We are grateful to CCsoft for giving us permission to
publish the object code and System Manual for this package, and to Gemini
Microcomputers for giving us permission to publish the Command Manual. The
documentation, therefore, is in two parts.
The System Manual.
This gives specific details for implementing Graphpac on the Nascom
and a summary of relevant commands.
The Command Manual.
This gives the general description of the commands and features
provided by all current versions of Graphpac.
Copyright and right to make backup copies
On receipt of this computer program and associated documentation, you
are granted a non-exclusive license to execute the enclosed software and to
make backup copies of the computer program for single user use only. Mbaslink
and Graphpac are subject to copyright and all rights are reserved.
No representations or warranties with respect to the contents hereof
are made and any implied warranties of merchantability or fitness for any
particular purpose are specifically disclaimed.
|NAS-GRAPHPAC SYSTEM MANUAL||Page 1|
NAS-GRAPHPAC SYSTEM MANUAL
This package has been introduced for the Nascom microcomputer to give
greater flexibility while controlling the low resolution graphics. It is
recommended that the user becomes familiar with the use of the Nascom system
and ROM BASIC before any attempts are made to run Nas-Graphpac. Nas-Graphpac
in fact consists of two modules, Graphpac, the graphics subroutines and also
Mbaslink which handles all the interfacing with the Nascom ROM BASIC.
Existing graphics commands (SET, RESET and POINT) are still available
while Nas-Graphpac is active, existing BASIC programs will therefore run
The MONITOR command will re-initialise Nas-sys by jumping to location
zero instead of doing an SCAL MRET.
This package requires a Nascom 1 or 2 fitted with the Nascom graphics
ROM and at least 16k of RAM.
The program is supplied in relocatable format and once configured for
the host system, it will be 2K in length and can reside anywhere in the memory
map above 4800 hex. (including ROM if required). Workspace RAM can optionally
be set at 0D00, 0E00, 0F00 hex or just below the relocated package.
COMPATIBILITY WITH OTHER SOFTWARE
Nas-Graphpac is fully software compatible with the Nas-sys series of
Monitors, however, because provision was not made for extending the command
table in the Nascom ROM BASIC it has been necessary to use the flexibility of
the Nas-sys monitor to achieve the interface. The method used is to copy out
the SCAL table from the Nas-sys ROM into workspace RAM. Various modifications
are then made to the entries allowing BASIC to link with Nas-Graphpac. Once
Nas-Graphpac is active on the system it fools the Nascom ROM BASIC into
thinking a non-maskable interrupt has occurred. Control then passes to
Nas-Graphpac via the Nas-sys SCAL table. As the SCAL table is copied into RAM
and modified, it is unlikely that other Nascom software that also does this,
will be compatible.
Because of the number of different system software and hardware
options available on the Nascom it is impossible to support them all,
Nas-Graphpac has therefore only been tested on a standard cassette based
system running an unmodified Nas-sys monitor. Having said this, we would like
to hear of successful interfacing to Polydos 1, Polydos 2, Nas-dos etc.
If Nas-Graphpac does not operate correctly on your system because of
software incompatibility with your uprated operating system, all is not lost.
A USR mode has been incorporated inside Nas-Graphpac and graphic commands can
be used via the USR function. See appendix 3 at the back of this document for
Load Nas-Graphpac into memory from the listing given at 1000 hex and
using the Nas-sys Write command make a tape copy. Decide where you want Nas-Graphpac
to execute on your system. Normally this will be in the top 2k of
available RAM which will depend on the size of your memory board and
whether you have system firmware in ROM (Nas-Dis/Debug or Zeap). Execute Nas-Graphpac
at 1000 hex followed by the address where the program is to
E 1000 7000 (enter)
will generate a Nas-Graphpac that will run at 7000 to 77FF hex.