Hi-Res (Software) Explained ?

[Rishi]

Ok Here's the new topic, I've altered my Ram-pack so that it should be able to deal with Hi-Res, but how to test this ? and where can i find a complete explanation of the different systems used ?

[olofsen]

Some useful links:
http://www.user.dccnet.com/wrigter/inde ... torial.htm
viewtopic.php?f=11&t=289
http://sinclairzxworld.com/viewtopic.php?f=4&t=1639

[Rishi]

I am, by now quite confused about all the HiRes, Maybe it is just to much info, although i suspect that part of the reason is that i wasn't into this at the time it was developed, and therefore don't see it step by step. Anyway as far as i can tell, there is 2 schemes (more or less) that work without any additional hardware. WRX and Mathias' s scheme. but these need additional drivers right. Is it just me, or is it just written down in a way that assumes quite a lot of knowledge. I want to test the small hardware modification, before i get into the nitty gritty. I thought i should try the 3dfrac , but i somehow seem to be out of memory !? i tried few other things, but i am at a loss. Let me get a little filosophical, The problem is that only computer programmers can write the manual, since only they understand sufficiently, but unfortunately they write these as if it is a computer program, it being as short and efficient as possible, therefore they get a little hard to read for me.

[olofsen]

Understanding how hires works exactly does indeed require a lot of knowledge on how the Z80 processor works, and how the processor is used to produce a display. One important thing is that the IR register combination should contain the address of the hires bit pattern. Getting IR to hold the right address at the right time requires knowledge of Z80 instructions and the timing of the ZX81. The familiar RAM modification with the diodes is needed so that when the IR is on the address bus, the hires bit patterns can be read from the RAM pack. (This didn't work with the pack I bought in the 80s, and it took me years to figure out how to fix it!) The same modification is needed for Matthias' drivers; there is a 16K and a 64K version. The WRX programs do not need a driver, just a hires capable RAM pack. Could you tell us a little bit more about the hardware modification you want to test?

[dr beep]

When you want to test hires without RAMPACK you can use ANY WRX-hiresroutine.

Just create a 256 byte buffer on i.e. #4200
Make a small screen from 8 lines with some graphics like UDG you set on each line.

Only thing you alter in the hires is instead of ADD HL,DE ( where DE often is 32) you will
LD A,L
ADD A,32
LD L,A

For timing you need you reduce the routine somewhere with 4 Tstates.
Worst case, take off 1 NOP in linebuffer, just showing 31 characters.

Your routine will then display 8 hires lines repeating until fullscreen

[Rishi]

Well The Ram-Pack i build consists of a 32K SRam, with Memory avaiable between 4000H & 7FFFH (standard 16K) and between B000H & FFFAH (the other half minus the final 4 addresses that are being used for a 32-bit interface) and because i had been using some logic gates to get the proper signal i used an AND gate to connect !REFSN && !RD, so if either goes low, the signal will go low.

Like this. Rather than using the method with the diodes and a pull-up resistor. The creation process was all at the end of the Bad Memopak thread, but since this was going in a different direction, i thought a new topic was better.

[Rishi]

Ah Sh....T now i see what i've done wrong, i should have wired up the !WR Pin not the !RD .... oh man, sometimes i wonder about me. okay back to the drawing board, pull the pack out of the box again.

[dr beep]

Hires by WRX-method

In program, set IX to hiresroutine

Hiresroutine:
Initialize start on screen with some delay
Set HL (most common) to start of HIRES
Set linecounter (most Common B)
Set I with H
Do call to linedisplay in uppermemory
Set R with L through A
Do display in higmem ( the NOPS) and go back to lowmemory
Adjust HL to next line
Repeat all lines
Some exitroutines for correct return to mainprogram

that's all, although 1 line of display must fit 207 Tstates.

[Rishi]

Yeah Hold-on, but have i got it wired-up right, looking at the topic again i think i have ? Before i start changing stuff.

[olofsen]

Well there's a 50% probability of 1 being 0, /RD being /WR, and EAR being MIC Let us know if for example WRX now works!