2019. január 26., 1055 Budapest, Nyugati tér 9. 14-19 óráig
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Messages - BruceTanner

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Hardware / Re: SD card interface
« on: 2019.January.01. 19:42:18 »
Coming soon: ZozoTools Clock included to SD ROM
Which bit of the ROM does it go in? How many bytes (v.approx)?

You know why I'm asking :mrgreen:

Hall of Fame / Re: Q&A with Bruce Tanner (IS-BASIC writer)
« on: 2019.January.01. 19:35:32 »
It wasn't any of the core IS developers, we were too busy with the important things :lol: :lol: :lol:

I think it was arranged by Enterprise Computers at the last minute, I only saw it when it was finished. Sorry I can't put a name to it! :oops:


:smt031 It is a very long time since I heard that sound! Happy New Year (even though you are making me feel old!) :smt031

Hardware / Re: GFX-NINE, the intruder graphics cartridge
« on: 2018.November.12. 10:10:54 »
If you can, I would also suggest you borrow a good oscilloscope and trigger on a brief low-high glitch on /RD with a threshold of 0.7V (a Rigol can do it) and see if it triggers...

Also always use a real 74LS245 rather than a 74HCT245 as CMOS (HCT) ICs can oscillate if their inputs float, as happens when the bus goes tri-state (I have seen it!)

Programming / EXDOS 3.0
« on: 2018.September.09. 13:42:21 »
A little taste / tease...


No promises, still quite a bit of work and testing to do... : Lol:

Programming / SHA-1 / HTTPS on a Z80?
« on: 2018.July.20. 14:47:40 »
For a while now I have been wondering how well a 4MHz Z80 would cope with some modern encryption protocols like those used for HTTPS web sites (ie most web sites these days), so I wrote some SHA-1 encryption code and a test program:


The .html file for the main page of  EnterpriseForever.com (which is also a HTTPS web site) is around 64k once all the secondary files are included. Based on my SHA-1 code it would take around 15s for a Z80 to decode!

There are more modern and more secure SHA algorithms with longer hash values but they operate in a broadly similar way.

Here is the source code for the SHA-1 algorithm in case anyone ever finds it useful (assembled using sjasm 0.42c). I was able to adjust the official algorithm a bit to avoid copying all the data twice!:

* sha1.asm (49.56 kB - downloaded 21 times.)

And here is the source code for the test program which includes the above file (sorry, a bit messy as it was hastily hacked together from another program!)

* sha1test.asm (15.19 kB - downloaded 17 times.)

Bitcoin mining on a Z80? :mrgreen:

Hardware / Re: EPNET
« on: 2018.July.12. 22:57:29 »
I was hoping not to have to write this, but sadly I have to report that EPNET is on hold for now because of an unusual problem I have had since last November: my house (and workshop) have been invaded by biting bird mites. I have spent a small fortune with pest control companies but nothing they have done has got rid of the mites. My strategy now is too stay away from my house as much as possible (ie. all day, every day) in order to starve the mites out (they are blood feeders).

It is an uncommon problem but it is clear from other peoples' stories on the internet that this could go on for months or even years. I am grateful that it does not threaten my health, but it has put my life on hold.

I am very sorry to anyone waiting for EPNET, and particularly to gflorez and zozo who have put time into translations, but there is nothing I can do at the moment.

I have put a lot of time and work into EPNET and it is very painful to have to abandon it, but I have no choice.

If anyone is in a position to continue the project or a related project I'd be happy to send h/w design files and s/w source code, and help with knowledge and expertise. I like to think I will continue it again in the future but currently I just cannot say when that might be.



Other topics / Re: ZX Vega+ new Spectrum games console
« on: 2018.June.02. 12:39:58 »
But hard to understood the lot of delays: just need to put the Vega to a new case, add battery and LCD, which are very popular components today...
Disputes among the company directors from what I read!

I have not followed the story of Vega much, it just caught my eye because of David Levy. It is definitely the same Mr Levy - there is a photo. Older than I remember from 30 years ago of course, but so am I :(

Other topics / Re: ZX Vega+ new Spectrum games console
« on: 2018.June.01. 23:45:42 »
Oh dear...lots of Levy-hating going on by disgruntled backers who have not received anything, shipping dates repeatedly being missed...sounds familiar! http://www.retro-computers.co.uk

Other topics / ZX Vega+ new Spectrum games console
« on: 2018.June.01. 23:15:52 »
The new Spectrum-like games console seems to be in trouble according to  BBC news story but scroll down a bit...look who one of the backers is...Dr Levy!

(Sorry if everyone already knew that, I didn't!)

Programming / Re: Easy relocatable code in basic
« on: 2018.April.26. 21:22:32 »
:smt041 :smt041 :smt041

Programming / Re: Easy relocatable code in basic
« on: 2018.April.25. 21:26:38 »
The real problem I found about doing relocatable code with the Z80 is the impossibility to read the PC register to know the address of the instruction the processor is actually executing.
Here's a bit of a wild idea if you know interrupts are enabled:
Code: [Select]
        DEC SP
        DEC SP
        POP HL    ; HL=address of DI instruction :-)

(untested :mrgreen: )

Hardware / Re: SE-ONE music file player
« on: 2018.April.20. 00:41:35 »
I know, I know, it could be done better and nicer.... But it is only a demonstration, a straight translation of the MSX Basic listing from Hans.
Yes, you should have got MSX Basic running on the EP! :mrgreen: :roll: :lol:

Programming / Re: My Youtube Programming Tutorials
« on: 2018.April.03. 20:13:56 »
This is how EXDOS gets around the z80 bug:

Code: [Select]
;    This is a public subroutine because it is called by RAMUNIT as well as
; by DISKIO.  It returns carry flag set if interrupts were disabled and
; clear if they were enabled.  Also it disables interrupts.
XOR A ;Push a zero on stack and pop it
PUSH AF ; back off so we can tell if it gets
POP AF ; overwitten with IRQ return address.
LD A,R ;Get IRQ state
RET PE ;Return if interrupts enabled
DEC SP ;If they appear disabled then check
DEC SP ; whether the zero is still below stack
OR A ;If not then interrupts must have been
RET NZ ; enabled so return with carry clear.
SCF ;Return with carry set to indicate

Hardware / Re: MSX slot
« on: 2018.March.13. 20:18:44 »
On an unmodified EP you can be sitting at the IS-BASIC "ok" prompt and remove the BASIC cartridge. Then you can plug it in again and carry on as though nothing had happened. :mrgreen:

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