NASCOM2

Nascom2

These uses a Z80 CPU

See:-

http://ccgi.dougrice.plus.com/cgi-bin/wiki.pl?Nascom_2_Notes

The NASCOM 2 site is: http://www.nascomhomepage.com/#TheNascomRepository

http://www.dougrice.plus.com/nascom2/JavaScriptNascom2/jsnascom.html - A Nascom 2 you can run in a web browser

I found a picture of my Nascom 2 from about 1984.

My Nascom 2

When I brought my Nascom 2 it came with the 16K memory card.

This had slots for 32K and people were adding another row or chips on top of exiting chips with the data in and out pins bent out.

A Floppy Disk

I brought a second hand 8 inch floppy disk drive from Display Electronics.

Wireless World had a design that used the Western digital 1771 Disk controller chip.

Eventually it could read and write 60 out of the 80. tracks.

Using a Battery Backed read only RAM to store the DOS

A 6116 2K ram memory chip had a switch on the R/W wire so you could save to it when presses, and it had a Ni-Cad battery backup.

Enough code to emulate the C and I instructions allowed specific sectors to be copied to and from floppy disk.

This was enough to read and write a sector to/from memory, and later it could do multiple sectors.

  E XXXX memstart_start  track sector   

This code was run from a 6116 2K RAM chip. This chip had a Battery Back up circuit using a NiCad battery and a switch on the RW line to disable unplanned writes.

So a bit of paper with the sectors and addresses recorded where the programs were stored was kept with each floppy disk.

Later the first sector stored a program and the list of files, and you could select and load a program.

It was a lot quicker to use than the cassette player.

Sometimes you had to reload the 6116 ram chip from a cassette tape was required as the Ni-Cad only lasted about a week.

This was quite fast as it read sequential sectors. You could replace the file if smaller, or append it on the end if bigger.

Golfball Printer

Printers were expensive in 1980.

I brought a second hand golf ball printer. To control it , you has to drive the 2x7 matrix of solenoids using the Z80 PIO chip.

The Solenoids needed about 50 volts, so one bit drove a transistor level shifter that selected the row of 7 bits.

A look up table was required to map the Nascom character set to the Print ball.

Some characters like ; needed the sequence : backspace then , to render them.

It took about 4 minutes to print a side of A4 and I needed a thick pad of foam rubber to stop the house shaking. A bit anti-social.

Eventually the clutch went, so that was the end of that.

I brought a dot matrix printer that was like the FX80 but was not. It could only print at 40 cps and was slow.

Conclusion

I was looking at how Tommy Thorn used the HTML Canvas for the display, so My Nascom is still providing learning opportunities after it was put in a friend's loft.