64 Column Zeddy.... Well maybe...

[Bill H]

Looking great! After you get it perfected you need to get lowercase characters in there.

[PokeMon]

That would be easy with my new memory kit where you can change the charset.
Just to put lower characters instead of the graphic ones.

[BrunoFlorindo]

I don't understand the details of the work involved but, couldn't you borrow some ideas from what Timex did with the TS2068, TC2048 and TC2068? These machines all had a special video mode that could be invoked when necessary. The mode changed the resolution to a monochrome 512×192 display. The idea at the time was to allow Sinclair users to use CP/M, but it could be used while using the Spectrum rom too. I remember I used to switch to the high resolution mode using OUT from BASIC, just to experiment with the 64 column display.

[siggi]

BTW: would a greyscale or even colour ULA be possible???
That would need a DA converter, but a 8 bit DA could be made using 8 digital outputs and 8 resistors ...

Siggi

[Paul]

BTW: would a greyscale or even colour ULA be possible???
That would need a DA converter, but a 8 bit DA could be made using 8 digital outputs and 8 resistors ...

Siggi

The spectrum color mode is without DA converter just having bits for red, green, blue and bright. This could be made compatible to the Lambda color module ...

If the c64 oops, I mean 64C mode would be compatible to the TS2068 512*192 video mode this would be great...

[Andy Rea]

oops, double post...

[Andy Rea]

Some more tweakage later... i sat down and counted t-states... And still got it worng but not by much.... NOT 100% perfect but i can live with that, slight warpage on first line....



Now to have a look at the load/save/plot/unplot/print AT/tab

Remind me whose idea was this 64 column thing

Ah grey scale / colour... well anything is possible, it's juat a case of finding a way to do it

Andy

p.s Don't forget this is running at a constant 6.5Mhz cpu clock, and 13Mhz pixel clock ( well 53.2 divided down)

[siggi]

Great work

p.s Don't forget this is running at a constant 6.5Mhz cpu clock, and 13Mhz pixel clock ( well 53.2 divided down)

So a "standard" new ULA could be used (with new code inside) and only a patched rom would be necessary to do this with a normal ZX81? Or is another quartz required for that ULA?

Siggi

[Andy Rea]

i think you would need at least a good ( near 50% duty cycle) 13Mhz at least, i can't do PLL to multiply 6.5 up can only do divides. ROM and RAM need to be able to work at the higher speed, my EEPROM is only just able to do the refresh in time....

and pin 16 of the CPU is bent out so that it misses the socket (INT pin) as R is loaded with values that already have bit 6 reset, so a new INT signal is generated when A6 = low, HALT = low, refresh = LOW, this avoids an int happening early on in the scanline, this is why i was going to leave this little side project because i couldn't at first see a simple way around this problem.

Fast no longer works... Well it does but the display is all over the place, blank lines are generated by waiting for the INT but CPU is already halted near the begging of the line, so we get an INT way too soon.... I'll think about this one....

patchinh the save routine is easy, the load routine not so easy how does one double $9f in a single byte

I'll think about that too....

Andy

[PokeMon]

Remind me whose idea was this 64 column thing

I am not sure.
What about the lines ?
If we have 64 columns we need 48 lines too.

Anyway, great work so far !