Search found 163 matches

by crankorgan
Wed Jan 11, 2012 1:37 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

Well I got rid of the ghost! I have no idea why having the 74HC251 turn on at 8K to 16K and 32K to 40K if a Poke is hit. Turning off the 32K to 40K killed the ghost. In any event I got the circuit working. Is it worth it? Some of the sounds of the SID make my one ear BUZZ. I am old and so are my ear...
by crankorgan
Tue Jan 10, 2012 9:12 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

Sir Morris, Use a hair dryer on it! Don't got too hot! Blow it out with a shop vac in reverse using the crevice tool. One of my 465B units has a digital voltmeter on top. The shipping is more than the scope. Sometimes I am the only bidder on Ebay. It is the type scope I had when I made the big money...
by crankorgan
Tue Jan 10, 2012 6:09 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

SirMorris, I collect 465 and B dual trace Tektronix Scopes. It might be a leaky buffer chip. I got my scope hooked up and I am about to re-hook just the address buffer and leds. With the ZX81 just sitting still the Address and Data Latches start the LEDS flickering. The SID plays a series of noises ...
by crankorgan
Tue Jan 10, 2012 5:07 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

I used the 74HC251 with my BBUM but in that case the Memory Chip has the WR signal. What I don't understand is how the signal comes out of nowhere and then stops. A few minutes later it starts again and then stops!
by crankorgan
Tue Jan 10, 2012 2:52 am
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

I have been tracking down the "Sinclair Ghost". Funny Huh? It shows up on my two ZX81s test board. The Ghost is coming from the output of the 74HC251. The 74HC251 only has four signals. A13 A14 A15 and MREQ. MY guess is MREQ is putting out signals every few minutes for about 60 seconds. Tomorrow I w...
by crankorgan
Mon Jan 09, 2012 7:00 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

Ok Sir Morris,
I will hunt the info down.

John
by crankorgan
Mon Jan 09, 2012 3:55 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

The one shot works! I also did a set/reset flip flop. The buffer latch signal goes to the flip flop. As it goes from high to low it flips the flip flop. The 1K system clock flips it back. That signal clocks the data into the SID (Synchronized with the system clock) Now the elephant in the room! ZX81...
by crankorgan
Sun Jan 08, 2012 9:22 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

Here is the TEST 64 program

10 poke 54272+int(rnd(1)*25),int(rnd(1)*256) : goto 10

54272 would be 8192 on my machine.
by crankorgan
Sun Jan 08, 2012 8:46 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

Andy, After the program has been stopped and the cursor is just sitting there. It is about five minutes each time. Then my address decoder starts putting out pulses that cause the latches to put out data. PastBytes, My latches are one way so there is no paddle input! As for hooking the SID to the ZX...
by crankorgan
Sun Jan 08, 2012 7:54 pm
Forum: Development
Topic: ZX81 driving a SID 6581
Replies: 68
Views: 29652

Re: ZX81 driving a SID 6581

I put in a one shot that gives me a 8us pulse to the /CS. The circuit seems to be working. Just one more flaw! The address decoder starts putting out pulses if the ZX81 sits there not running for a few minutes. This is my second ZX81 that does this! Is this the Ghost of Sinclair? At this time I will...