Sinclair ZX80 / ZX81 / Z88 Forums

Hi. Thickness = 1.9mm Width of the strip (ie. front to back) = 19.7mm length of piece touching PCB = 32.2mm (from left hand side to the right hand side of the bend) Vertical = 20.5mm (from the bottom edge touching the board to the top edge of the top horizontal piece) length of top piece = 19.8mm (f...

Hi. It's supposed to be really quiet - it is designed to be plugged into a VERY sensitive mic input of a tape recorder. The mics produce a very low signal (ie. the dynamic "moving coil" ones found on the old cassette recorders) so the signal has been greatly reduced to match the level expected from ...

When I "prod" about with a scope probe, I normally use the x10 setting on the probe, and increase the sensitivity of the scope appropriately. The x10 setting puts a 9Meg attenuator resistor in series with the probe tip (scopes have a 1Meg input impedance) and drastically reduces the effective capaci...

Hi Retrotechie.
Yes, that's correct. Stretching only occurs during the "NOPed" execution.

Regards.

Grant

No probs Andy - that is what I saw first of all - and it confused me for some time :) Here is a pic that I posted earlier in this thread before I filtered out normal program execution statements: OscPic1.jpg I have annotated it here to show the normal prog and stretched DFILE ROM CS. The scope pic t...

Hi Andy. I think all signals seem to match except for ROM CS. I set the scope triggering to occur mid-line with a fully expanded DFILE. Also, using an LM1881 and some extra circuitry, I was able to eliminate the non-display parts of the screen, and therefore eliminate "normal" program execution stat...

I've done an 80x25 display from an ATMEGA, but never seen a complete emulation of a machine on one !

Impressive.

Grant

I think I'm making progress... I installed both the Altera and Xilinx software dev and did a crash-course / Google to get me running with the VHDL. After the first couple of blocks of code it started to get easier. A bit worrying when I first put in some of the blocks of code, as it said I only need...

Hi Andy. I realised the same last night :-( I counted the pins, and there aren't enough IOs with the 44-pin Xilinx devices. I was going to skip the USA/UK as it's not needed, but I wanted the cassette. The alternative was to off-load the keyboard read to a seperate chip (as on the ZX80), and just ha...

Thanks for the info, Andy.

I'll put a Farnell order in shortly

Regards.

Grant