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The AY Datasheet unfortunately doesn't mention what current the pins can supply or whether there is currrent limitation on the pins. If the Telecharger software is written properly, it should turn off the 74LS145 scanning while sending data, otherwise an accidental keypress would cause exactly what you are describing. As the 74LS145 is controlled by the 8255, setting the BCD inputs to 1111 essentially closes the path to ground for all 145 outputs.

Hi Bryce,

Thanks for your schematics and information.
To my knowlege, only "amcharge" might have set the PSG I/O port as an output to control the download of softs from the french minitel network [1]

Still (for the sake of education) speaking about the keyboard now, am I right to say that  a relatively high current might flow from a PSG I/O pin to a 74LS145 OC output pin in the following situation ?
- PSG set as output (unlikely, but possible)
- Key pressed (circuit closed)
- 74LS145 output line grounded (OC transistor saturated - which happens when a keyboard line is selected for read)

Demos / X-Mas 2010/Merry Christmas 2010 by Impact
« Last post by ComSoft6128 on Today at 11:39 »

It's getting close.....
Festive French demo which features a nice screen and a lovely toon!
CPCPOWER has the music running to 4:33 but I let it run just a little longer.


Not emulated - original hardware and software.
Please note that  the aspect ratio for this YouTube video is 16:9 but the CPC monitor
has an aspect ratio of 4:3 so you may wish to adjust your viewing device accordingly.

Question: how many of you had connected the CPC to an external amplifier?

I did in 1990. I bought a 3.5" to Aux cable and plugged it into the back of my stereo. I had 4 speakers on it (I connected two to each channel) and Space Harrier sounded amazing with the volume cranked up!

Really ? :) I can still remember the original Amstrad 3" discs - the red/white Amsoft ones - as being reliable, yes. But the other brands - usually cheaper - were crappy in my experience and it was frequent to me back then to get many read fails etc. on those.

Yep, there were some awful "ex software house" cheapo discs that did the rounds and I'd say they lasted about 10 successful writes. There definitely was cheaper alternatives out there and they were complete rubbish.

I only wish I knew about the multimark tool back in the day! :D
The joystick pins are never set to be outputs in any normal situation and no game or demo I know of does this, so there is very little chance of damaging your device. As far as setting the pins is concerned, this has to done by shorting the pins to COM not to ground, so you can't use standard logic to pull pins low. On my AMX Mouse interface I did this by setting the inputs on a 74LS240 buffer and connecting COM to output enable. This way the joystick pins are only pulled low during the low pulse on the COM pin. You can see the circuit here:

Most of this circuit could be used as the basis for a joystick adapter.

Programming / Re: CPCRetrodev 2021 : Fitzroy Dives Deep
« Last post by Arnaud on Today at 09:08 »
I have not to reproduce the problem, but when in your menu you can just set  :


to simply just not to call playSound() in your interruption.

And when game start, put the right value :

soundMode = SOUND_MODE_ON;

Thus not need for the function PLAYER_ARKOS_STOP()
Seems a bit wierd that the Gotek software would do things this way, but I suppose that Gotek doesn't know that it's working with a PCW system, and another system might need to do the double step?

How the Gotek does it (assume by default that all disk images have the same track spacing as the drive) is the most obvious and useful way to behave for nearly any system. It just doesn't get on well with PCWs, where the system software expects the same disk (image) to give different results in A: and B: - particularly difficult if both are identical Goteks!
Programming / Re: Transparency in BASIC
« Last post by eto on Today at 01:51 »
Kind of worked. The transparency worked - Thanks! But the pen colour did not as the MOVE command does not have a 3rd parameter. According to the CPC464 manual it only has two - X and Y.

I forgot that... In my game "Cameronne" I also use TAG to write text in a custom font (4x5 pixels) to the screen. I quickly checked the code and I use e.g. PLOT -2,-2,13 to set the graphics pen to 13. I remember that I had problems making the game compatible with the 464 because of some missing commands and that I recognised that PLOT has the third parameter to set the graphics pen on all machines in the same way. -2,-2 is outside the screen so it won't be visible but it still sets the graphics pen.
Emulators / Re: Why does BASIC add a space?
« Last post by ralferoo on Today at 01:47 »
It's weirder than just setting N=&9FDF and then doing N=N+1 and GOTO.
Emulators / Re: Why does BASIC add a space?
« Last post by Johnny Olsen on Today at 01:21 »
Also, if you look at the logic at the next part, the author is using 1E+09 to effectively mean infinite, and then checking the string for END to terminate the loop. Weird because it relies on the NEXT being run as part of the conditional, but it should work fine.

Not wierd. This poke almost ruins the game, therefore you have the opportunity to leave out
some of the cheat eg delete line 200

if you had loop like this
100 FOR N=&9FDF TO &A081:READ A$:POKE N,VAL("&"+A$):NEXT
you will get an error message "DATA exhausted in 100" if you deleted some DATA.

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