Search found 1557 matches

by Andy Rea
Tue Jun 17, 2008 9:43 pm
Forum: SALES
Topic: Non-Working ZX81
Replies: 3
Views: 4875

Re: Non-Working ZX81

Hi Rich,

you do paypal don't you ? PM me your details and cost and i'll do it straight away

Regards Andy
by Andy Rea
Mon Jun 16, 2008 4:47 pm
Forum: Development
Topic: RAM at 8-12, EEProm at 12-16k
Replies: 29
Views: 17150

Re: RAM at 8-12, EEProm at 12-16k

Because of incomplete memory decoding in the ZX81 only using /Mreq and A14 means that internal rom is enabled by default from 0-16k address range. therefor if we want our rom/ram at that address range (or part of) we need to disable internal rom at our selected range. Andy LOL i should have read pag...
by Andy Rea
Mon Jun 16, 2008 12:06 am
Forum: Emulators
Topic: Firm Zeddie
Replies: 10
Views: 9473

Re: Firm Zeddie

:lol: me neither. i've started but before i get into it too far since as your going to be doing the hardware side of it this is what i have for the pins struct pin { bool Level; // true = high, false = low int mode; // 1=cpu controls state, 0 = tristate, -1 = cpu expects to read pin, -2 input (fixed...
by Andy Rea
Sun Jun 15, 2008 7:55 pm
Forum: Emulators
Topic: Firm Zeddie
Replies: 10
Views: 9473

Re: Firm Zeddie

Okay dokeys, been thinking about this for a while and i'm ready to give it a go... A Z80 core Function that will excute 1/2 Z80 clock cycle on each successive call and set the 'Pins' to the respective logic level at each 1/2 clock cycle. of course Databus will have to have either an extra bit repres...
by Andy Rea
Sat Jun 14, 2008 10:19 am
Forum: Development
Topic: RAM at 8-12, EEProm at 12-16k
Replies: 29
Views: 17150

Re: RAM at 8-12, EEProm at 12-16k

Good Point.

Thanks Siggi

Regards Andy
by Andy Rea
Sat Jun 14, 2008 8:37 am
Forum: Emulators
Topic: Firm Zeddie
Replies: 10
Views: 9473

Re: Firm Zeddie

Well Cmos Z80's can be clocked right down to Zero hertz without harm, but it does say to reduce currrent consumtion you should first put it in halt state, but hey who cares about current ! as for the ULA i don't really know what would happen with that.... so perhaps the best way to go would be with ...
by Andy Rea
Sat Jun 14, 2008 8:12 am
Forum: Development
Topic: RAM at 8-12, EEProm at 12-16k
Replies: 29
Views: 17150

Re: RAM at 8-12, EEProm at 12-16k

Okay dokay

here is 1 chip version ! uses a few other components as well,

Regards Andy
by Andy Rea
Fri Jun 13, 2008 12:20 am
Forum: Development
Topic: RAM at 8-12, EEProm at 12-16k
Replies: 29
Views: 17150

Re: RAM at 8-12, EEProm at 12-16k

LOL i'm such a dummy ! never even considered /MemReq or /Refresh !

Going bed to get some rest and will draw better hopefully correct circuit tommorow :lol:

Andy
by Andy Rea
Thu Jun 12, 2008 10:50 pm
Forum: Development
Topic: RAM at 8-12, EEProm at 12-16k
Replies: 29
Views: 17150

Re: RAM at 8-12, EEProm at 12-16k

Decoding using 2 chips, use 2732 and 2 off 6116 or similar. just knocked it up off the top of my head...(spotted 1 mistake already need a signal diode between the edge connectors /ROMCS and the output of the INVERTER !) rush rush rush..... http://i243.photobucket.com/albums/ff60/andy_rea/romram.jpg ...
by Andy Rea
Thu Jun 12, 2008 10:04 pm
Forum: GAMES
Topic: Ball Blaster
Replies: 24
Views: 11848

Re: Ball Blaster

Very Nice, really good usage of the zeddies graphics, lovely and smooth, didn't really get it at first but after i read your instructions again much clearer, one of those 'Just one more go' games to try and beat your prevous score.

Regards Andy.