Sinclair ZX80 / ZX81 / Z88 Forums

Hi,
Attached the docs of a ZX81/TS1000 EPROM I/O programmer port, that I was able to interface to a PC.
I'd be interested in any comments . . .
b

Does this device use an 8255 IC?

DesSony

5) I/O CONTROL — performs single 8255 I/O operations. The seven
operation mnemonics are: WR PA, WR PB, WR PC,CNTRL, RD PA, RD PB, and
RD PC. For WR and CNTRL operations, data will be requested; for RD
operations, data will be displayed in parenthesis.

Another card here based on a 8255 : http://zx81.ordi5.free.fr/brico/ui/
("Micro-Systeme" 1984,Nov http://fr.1001mags.com/parution/micro-s ... embre-1983 )

dessony wrote: ↑Wed Jul 03, 2019 7:13 am Does this device use an 8255 IC?

DesSony

dessony,
Yes, and here is the schematic to see how the hardware is wired . . .
b

I have 2 EPROM burners for the 81 . One uses some kind of cobbled together logic chips and the other one is an 8255 device which can burn most of the old 21/25v devices when attached to either the 81 or the spectrum although I only have the spectrum software to run it(the guy who sold me it said it would come with the 81 software but came in fact with the speccy software!)

I use it to burn what ever new 81 ROM comes to the forum and have no need for PC burners which seem to struggle with the 21/25v end of things, I guess I'm a bit old fashioned when it comes to things like this.

Moggy wrote: ↑Fri Jul 05, 2019 10:29 pm I use it to burn what ever new 81 ROM comes to the forum and have no need for PC burners which seem to struggle with the 21/25v end of things, I guess I'm a bit old fashioned when it comes to things like this.

That’s because some of the cheap PC EPROM burners were originally designed to burn chips for automotive use and not old computers...
The problem with them is in the design and construction quality of the DC-DC converter. Where an external power input port is available, and they can take an external 12V DC input, they may then manage to program 21/25V EPROMS.

Mark

1024MAK wrote: ↑Sat Jul 06, 2019 12:49 am

Moggy wrote: ↑Fri Jul 05, 2019 10:29 pm I use it to burn what ever new 81 ROM comes to the forum and have no need for PC burners which seem to struggle with the 21/25v end of things, I guess I'm a bit old fashioned when it comes to things like this.

That’s because some of the cheap PC EPROM burners were originally designed to burn chips for automotive use and not old computers...
The problem with them is in the design and construction quality of the DC-DC converter. Where an external power input port is available, and they can take an external 12V DC input, they may then manage to program 21/25V EPROMS.

Mark

Excellent explanation as always Mark, many thanks for that.