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I just used something like these.

Sorry for how long this has been taking. Life throws you some real curves and fast balls once in a while.

In any case, the RAM/EPROM board is now working and tested.

Here it is on my 600B



I loaded a BASIC5 ROM image Mike (MK14HAK) sent me into a 27C64 and booted it up. Works great!


Basic 5 only seems to take up an extra 2 bytes of memory - nice>


The code For the GAL has been loaded up in post 1 of the thread.

If anyone is interested in one of these boards just PM me. I'll put them up on my web site soon too for folks in the US and Canada.

Just brilliant ! My order on the way thanks Bill.

Nice see someone else using the Premier ROMS - good potential here for some easy program editing with Toolkit and using Cegmon windows with the extended BASIC commands.
I have more code coming that makes the system even more flexible...

PS no noise in that video ?

After Bill had kindly reminded me that the expansion board actually needs a power supply by bridging +5V to pin 11 of the expansion socket, the memoy expansion board now works!

Thanks, Bill, this is really great!

Stephan

Nice! Glad to see it up and running!

MK14HAK wrote:PS no noise in that video ?

Not on that TV anyway. I can see some on my old analogue monitor though. The wonders of the digital age, eh?

Anybody had success with I/O connected on the expansion socket of either board ??

...verified OK using DDIN not DD with 470B.

After a few days spent de-oxing connectors, scoping signals etc, I finally have a RAM/ROM board working with a temporary connection to the OSI bus on my SKIT502. The RAM worked at first power up but the ROM read incorrectly. This lead me to suspect the connectors on the 502 card. Sure enough I located and fixed two high resistance paths but still the ROM data was wrong. Add to this the 470B controller that works fine on my 600RevD would not boot.
Related ? Yes. Closer inspection of the ROM data showed all the $20 JSRs as $DF. The 600RevD uses 8T28s and the 502 inverting 8T26s ! I wasted a few hours finding this and nearly had the LAP-C hooked up.
Should have looked more closely at the cct diags.
Invert the ROM code using HxD and I now have Exmon, B5,TKit and my User routines available, 32K RAM. Thank you Bill.

PS. Note, a small signal diode is required on the DD line also. (Pin3 on the 40PDIP if you look closely)

Jeff wrote:
I wonder if this can also be adapted to the C4P. I have one of those with only 8K as well!

/Jeff

The RAM will work fine on a C4 but to use the ROM the code needs inversion or the board needs 8T26 inverting buffers.



Next up is a small mod and a re program of the GAL to see if I can use a DS1643 NVSRAM/RTC in place of the ROM. And a version with 8T26 buffers 48PBUS connectors and sound. (anticipated "light of day" 2016 !)

... The 470B is still not booting on the OSI bus after a buffer swap ?? http://osiweb.org/osiforum/viewtopic.php?f=3&t=284

I have a working 32K RAM expansion board, and now I'm looking into attaching a further peripheral to the expansion socket on top of the memory expansion board.

My question is, how must the DD line be implemented so it doesn't interfere with the DD signal of the memory expansion board?

From the thread Questions about data bus buffers and DD signal I know already that the peripheral must drive the DD line low when a read from the peripheral occurs. But how must the peripheral handle the DD line while it is not addressed?

Thanks
Stephan

The device operating the DD line must be open collector or open drain. The DD, when used with the 32K RAM board is pulled high by a resistor on the 600 board so you cannot use a device with an active pull-up.