Sinclair ZX80 / ZX81 / Z88 Forums

Posted: **Mon Sep 23, 2024 8:45 am**

Hi,

I plan to build a new extension card to grab the ZX PRINTER IRQ to preview the screen copy or to do a fast print.

Is there any little screen in 256*192/300 easylly driver without an ARDUINO or other Rpi software library ?

Just driven by the ZX81 dot flow.

It will by a ZX SPECTRUM compatible device, able to print the Memotech HRG drawing and can display ZX Printer UDG/HRG.
This card, will able to switch to the ZX printer to print the final ZX PRINTER picture.

Thanks in advence for suggestions.

Posted: **Mon Sep 23, 2024 12:18 pm**

I don't know any.
I always use 320x240 screens that are widely available.

Posted: **Mon Sep 23, 2024 6:04 pm**

Hi Paul,
i can add an internal counter to jump to the next line at the row 256...
I will explore this idea !
Some primitive drivers don't waite the and of line...

The ZX printer data decoding (WIP):

ZX81_VitualPrinter.pdf: (151.39 KiB) Downloaded 212 times

Posted: **Mon Sep 23, 2024 10:11 pm**

Hi,

The counter is ready, but...
due to incomplete decoding of the printer output, the counter will be shifted by one pixel at initialization... so the image will be displayed at an angle on the screen and I don't have an answer to test the initialization period at the moment.

We had to ignore this OUT command:

Code: Select all

		XOR	A
		LD	E,A
087D COPY-TIME	OUT	(+FB),A ; <<<<<<<<<<<<<<<
		POP	HL
0880 COPY-BRK	CALL	0F46,BREAK-1
		JR	C,088A,COPY-CONT
		RRA
		OUT	(+FB),A
0888 REPORT-D2	RST	0008,ERROR-1
		DEFB	+0C
088A COPY-CONT	IN	A,(+FB)
		ADD	A,A

Any ideas ?

ZX81_VitualPrinter_counter.pdf: (197.16 KiB) Downloaded 166 times

Sinclair ZX80 / ZX81 / Z88 Forums

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