Sinclair ZX80 / ZX81 / Z88 Forums

Thanks Sir Morris! After I added the inverter to my latch signal to make the /CS the circuit got funky. I suspect I need a pullup resistor. I went back and put in a transparent latch on the data and kept the edge triggered on the address. When you hit a Poke you can see the address lines show up and...

If I run

10 POKE 8216,15
20 PAUSE 10
30 POKE 8216,0
40 GOTO 10

I hear the Volume poping up and down but not evenly. It is hit or miss. After I put in the onshot I will adjust it so every /CS is long enough to clock the data in! Wish me luck!

Pastbytes, The new circuit let out a noise! I need to make the /CS pulse longer. I have an inverter on my latch signal to make the /CS. I had to go to a neighborhood meeting. Now I have to get dinner. Then I will add a one shot to the /CS signal. I used POKE 8196,15 Volume High POKE 8197,190 Envelop...

Pastbytes, On a Commodore 64 (in BASIC) you Poke 54296,15 to turn up the volume all the way. The base address is 54272. So if you subtract the Base of address from 54296 you get 4. So a Poke 54296,15 becomes 4,15 4 on the Address Register lines and 15 on the Data lines. OR in binary 00100 on the add...

Short on output buffer. I used the type of perf board with traces on the back. I cut unwanted traces but of course a teeny tiny piece of copper held on! I got the LEDS working a 1-2-4-8-16-32-64-128 pattern With 8 different pokes. This works off a BASE number of 8192 just like the commodore 64 does....

Pastbytes. I have a program running. It does a Poke 8192,0 Poke 8193,0 Poke 8194,0 Poke 8195,0 Poke 8196,0 Poke 8197,0 Poke 8198,0 Poke 8199,0 When it goes to Poke 8200,0 It goes bad. I can also do 10240,0 ETC and it works 8 address. It is trying to tell me something. Maybe my buffer board is wired ...

Pastbytes, I am rewiring on my new Proto Board. The old one is worn out! I also swapped the Transparent Latches (74HC373) to standard Edge Triggered 74HC273. My first circuit that used three latches and three Poke locations worked. I have a complete 64 system. I like my ZX81 better because it is har...

Pastbytes, The SID needs some clock cycles in order to move data from the address and data lines into the SID. I wanted to make sure clean DATA was there to be clocked into the SID. The Commodore 64 SID runs off the system clock so it works. In this case I have a 2K clock into a flip flop giving me ...

Getting the address lines to latch out during a Poke is harder than I thought. One circuit works until it heats up! The circuit has to latch out the address lines from 8192 to 8216. So a Poke 8192,8 would produce an address of 00000 and Data 00001000 I need a break! I just called and old friend and ...

The LM386 wanted 12Volts to work. Now I got it working at 5volts.(go figure) I got the ZX81 driving the SID using my Christmas tree light circuit. Poke 8192, something Does the Address Poke 10240, something does the Data and a Poke 12288, one then zero shifts /CS on and off shifting the address and ...