80-Bus News


July–August 1983, Volume 2, Issue 4

Page 22 of 55


EV Computing writes: “Our IEEE card uses port FF hex for page mode switching as well as the ports 34-3F as correctly shown. We apologise for this error on our part.”

Lucas Nascom

Mike Hessey of Lucas Logic writes: “Please find attached a list of the I/O ports currently being used by Lucas Nascom. Other future products may use port numbers mentioned on this list. All these boards can be used with all other Nascom boards.

Nascom 1 – ports 0-2 & 4-7. No alternative ports. Uses NASIO. Requires buffering for connection to Nasbus.

Nascom 2/3 – ports 0-2 & 4-7. No alternative ports. NASIO is not used. No restrictions.

Input/​Output Board – 8-B & 10-12 & 14-1F. Alternative ports: All addresses can be selected via on-board links. Potentially could access any I/O address via A7-A0. Second board would normally use addresses up to 2F. Requires interrupt daisy chain.

FDC Board – E0-E3. Selectable to 20-23, 40-43 etc.

AVC – B0-B2. Screen memory is paged in automatically by graphics support software, normally at 8000 (link selectable). Requires use of RAM disable.

RAM B – Port FF output used for page selection.”

Well, Mike, I hate to contradict you (honest) but:

a) Surely NASIO is used on N2 & N3 when there is external I/O? After all, there’s a switch on the PCB to select between NASIO internal/​external.

b) The I/O board circuit diagram I saw implies 8-B & 10-1F are decoded.

c) The FDC circuit diagram I saw implies E0-E4 R/W and E5 R/O, and so does the customer below.

Sound and FDC

Mr. A. Brown writes: “I wish to supply the following information–

Easicomp Sound Board –Port2,writeonly,port3read/​write,or
"10"""11"I/O provided

Lucas Nascom FDC Board – E0-E5. I/O provided.”

Animation Graphics Board

Mr N. Crook writes: “The R & EW Animation Graphics board for the Nascom (Nasbus) (R&EW Jan. ’83) uses ports 08-1DH inclusive as far as I can tell from the article. Although I do not have one I know several people at NASTUG who are building then.

“Your ports map is coming in useful for me since I have finally started the design of my own I/O board (blow the dust off the prototyping board!).”

Isn’t this the same board mentioned by Mr Moyle above? If so then there is a contradiction in the port requirements for this board between their letters. Oh well, if anyone else has any more corrections to make, or new boards to add then please write in. I hope that I will have sufficient accurate information by the time the Nov-Dec ’83 issue goes to print to provide a “this is a state-of-the-art port map of the 80-BUS at the end of 1983.” For some reason I had imagined that this would be a simple job, but with some people being unwilling to supply any information and others supplying contradictory information I am beginning to think that I let myself in for somewhat more than I expected! Never mind, I won’t need to bother after 31/12/83 as it will be 1984 and Big Brother will be watching over everyone for me.

Page 22 of 55