ScreenCopy

by B. Johannessen

After reading an article in Computing Today written by Don Thomasson, I got an idea to write a program which can copy the contents of the Nascom screen directly to an Epson MX80 F/T type 2 printer by means of ‘Bit Image Mode’.

Graphics and alphanumerics are directly transferred and you can choose between black on white or white on black.

The usual MX80 F/T type 1 may only be used if it is equipped with GRAFTAX. The GRAFTAX may need some other initialisation.

The first thing to be done is to place a copy of the Nascom Character and NAS-GRA EPROMs into the Nascoms memory space. In my case it resides from 9000H to 9FFFH.

The main program resides in ROM from A000H . To start the copy I have used the L command in Nas-sys and altered it to point to A000H and if I add an ‘F’ as ARG1, the copy will be inverted. The program can also be called from BASIC with a USR routine call to A003H.

The problem I had in writing the program was that the Nascom characters have 16 lines and the printer only has 8 needles in ‘bit image made’. The printer has to go 2 lines for each Nascom line so I had to use a buffer to store the ‘bit image’ of one Nascom line before it is sent to the printer.

The program contains its own printer routine since my usual routine rejects linefeed code 0AH.