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#1
Quote from: Benedikt on 16:41, 30 May 24What would happen if we replaced all occurrences of ED 71 in RAM with ED 70 and added a pull-down resistor network to the data bus?You would break all code which uses ld (hl),c (&71) after an instruction that uses &ed as an operand, for example ld a,&ed -> &3e,&ed.
You would also break all code which happens to jump to (jp or call), load from or store data at &71ed, like ld a,(&71ed).
You would probably also break more code of which I am too lazy to think about.
And you would invalidate all data which happens to contain a sequence of &ed &71 for whatever reason.
#2
Quote from: Benedikt on Yesterday at 18:43I am curious: Would this still work if...https://www.falstad.com/circuit/circuitjs.html
is free for all !!!
#3
Ja...
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#4
Wollte gerade schon nachfragen...
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#5
B
Amstrad CPC hardware / Re: Zilog Z84C0020PEG in my CP...
Last post by Benedikt - Yesterday at 18:43I am curious: Would this still work if M1 and IORQ were latched on a clock pulse/edge?
If so, this could also work with a slightly more period-accurate ATF16V8 GAL controlling the bus transceivers.
If so, this could also work with a slightly more period-accurate ATF16V8 GAL controlling the bus transceivers.
#6
When I look at the KC compact's schematics, the only oddity I see in the palette circuitry is that the palette RAM is single-ported, which the system tries to mask by interrupting the clock signal to the RGB output latch whenever you write to the palette RAM.
I.e. you get repeated pixels on screen rather than much more annoying arbitrary snow artifacts.
The only two explanations I have for wrong colors are
As far as emulators are concerned, I believe that Arnold might be quite accurate, because it has quite a few source files for KCc-specific hardware components.
I.e. you get repeated pixels on screen rather than much more annoying arbitrary snow artifacts.
The only two explanations I have for wrong colors are
- Wrong values in the color translation EPROM, e.g for undefined indices
- Flaky hardware
As far as emulators are concerned, I believe that Arnold might be quite accurate, because it has quite a few source files for KCc-specific hardware components.
#7
Don't know if you are using Visual Studio Code for programming but there's a really cool plugin for installation available which not only let you program assembly but also go into debug and emulated mode for a CPC and KC compact.
Maybe it helps?
Maybe it helps?
#8
Quote from: chinnyhill10 on 21:31, 19 September 24Quote from: Bryce on 20:05, 19 September 24Trust me, I keep mine clean on the daily drivers. But unplug and replug and the CPC (or Speccy) edge connector needs another clean. Never seem to have the same issue on the drive connectors (again both on the CPC and +3).Quote from: chinnyhill10 on 19:55, 19 September 24Like the Div on the Speccy, the M4 seems to demand that your edge connector be very clean. I've never been clear if this is due to the demands of the devices or tiny differences when mating modern to old edge connectors. Either way DeOxit Gold is your friend.
It doesn't really have anything to do with any electrical "performance" requirements, the signals are simple, relatively slow, low current 5V connections. It's just because old computer connectors, especially ones that haven't been used for a while will be heavily oxidised, so the connections will be bad and the signals won't get through at all if the oxide layer is thick enough.
Bryce.
The Centronics connector definitely gives a better connection because it keeps more pressure on the contacts compared to edge connectors. The edge connector to the floppy drive is slightly more reliable because it's shorter and puts slightly more pressure on the contacts because of this. This pressure also helps to "cut through" the oxidation when you connect it.
As far as the "gold" is concerned, it's obviously better than the solder covered connections that were used up to the 70's, but it's not really gold. Real gold doesn't oxidate, but the coating is far from that. It's called ENIG in the PCB industry and it's done with a very quick dip in a chemical solution of gold and nickel, but this doesn't 100% coat the surface and there is a lot of exposed copper in the gold that will still oxidise and cause problems. On modern connectors / PCB's a newer process is used called "ENEPIG" which uses Palladium and nickel instead of gold and is more robust.
Bryce.
#9
I looked at FutureView I and II (correct ones to look at?) and I don't see anything with the code which would cause this problem.
What is the h/w configuration of the kc compact that shows this issue?
Also you say sometimes this happens on kc compact and sometimes not? Is there any way it shows more often?
What is the h/w configuration of the kc compact that shows this issue?
Also you say sometimes this happens on kc compact and sometimes not? Is there any way it shows more often?
#10
Quote from: zhulien on Yesterday at 03:15Some programs on cpc when you simply cat display an whole screen of stuff, is that executing anything from a boot sector or is it careful use of control codes?CAT never loads and executes a boot sector. It just displays the chars of the files using "TXT OUTPUT" (#bb5a) which will execute control codes as well. There were already tools from the 80ies for modifying a directory in a way that will display colourful chars placed at any location on the screen by adding dummy file entries with 0KB sizes. Or you hardcode it directly by yourself, which allows much more chars and effects.
The trick is to disable text output at the end of a filenam to prevent printing file sizes/line feeds and enable it again at the beginning of the next filename; and you also have to use one hidden char for sorting them in the correct order.