Search found 685 matches

by mrtinb
Sun Apr 29, 2018 2:02 pm
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

Ok... 3 changes in ROM. #0039/#003A becomes JR NZ,SCANLINE #003B is NOP , due to absolute jump to address of scanline, stays NOP #0046 1 tstate too much.... so this becomes NOP You are hereby officially declared: The Master that Knows ZX81 ROM by Heart in Sleep. It works great. (The 1st line looks ...
by mrtinb
Sun Apr 29, 2018 12:39 am
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

Perhaps it is the INT routine? The routine in the ZX81 compatible Lambda ROM is I think slightly different from the normal ZX81 INT routine which the ZXpand is using? Thanks for your feedback. I'll try to look at the disassembly of the ZX81 ROM, the Lambda 8300 ROM and the modified ZX81 ROM for Lam...
by mrtinb
Sun Apr 29, 2018 12:02 am
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

Code: Select all

AND 18h    7 T-states
ADD A,1Fh  7 T-states
changed to

Code: Select all

RL A      8 T-states
LD A,37h  7 T-states
giving 1 more T-state. But it did not solve it.
by mrtinb
Sat Apr 28, 2018 11:28 pm
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

Reading further in the book it seems that T states = clock cycles.

So it seems I need an extra T state in the loop that draws the line.

I was hoping to have the same ROM in the ZXpand for both ZX81 and Lambda 8300, but that seems down the drain now.
by mrtinb
Sat Apr 28, 2018 11:21 pm
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

I seem to remember something about the Lambda using 208 cycles per line, whereas the ZX81 uses 207. This is strictly a vague feeling, not something to rely on... I don't know much about timing on the ZX81 and the Z80 processor. I do however have Rodnay Zaks Programming the Z80 where is states that ...
by mrtinb
Sat Apr 28, 2018 11:02 pm
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

What picture do you get from loading 1 of my 1K hires games? This could determine if it is lowres or hirescontrol (timer per line). The jumping text is what I had too when writing lowres too soon (not enough NL) to the screen. I've load Humpty 1K in this video with the ZXpand ROM: https://youtu.be/...
by mrtinb
Sat Apr 28, 2018 9:46 am
Forum: Development
Topic: To Masters who knows ZX81 ROM by heart in their sleep
Replies: 1
Views: 210

To Masters who knows ZX81 ROM by heart in their sleep

I know most of you is not as enthusiastic about the Lambda 8300 as me. And therefor have skipped the discussion in the Lambda forum below. I'm asking for help to change the ROM to not test for PAL/NTSC but simply hardcode it for PAL. I've hardcoded the MARGIN read to $37 but unfortunately that is no...
by mrtinb
Thu Apr 26, 2018 8:38 am
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

As you can see, the picture is difficult to read.

This is a picture of the ZXpand Commander.

Image
by mrtinb
Wed Apr 25, 2018 10:05 pm
Forum: Hardware
Topic: ZXPAND and Lambda 8300?
Replies: 28
Views: 4257

Re: ZXPAND and Lambda 8300?

I want to hardcode the ZXpand ROM for PAL, as the Lambda 8300 has a different PAL/NTSC detection. I changed 02DF: ADD A,1F to 02DF: LD A,37 This makes MARGIN be $37 always which I can read in the disassembled ZX81 ROM is for UK (PAL). The two statements have the same 7 T-states, so timing should be ...
by mrtinb
Tue Apr 24, 2018 8:08 pm
Forum: Sinclair Misc
Topic: Screen highlighting ZX81
Replies: 2
Views: 252

Re: Screen highlighting ZX81

Exactly. Thank you! :-)