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Messages - dangerman

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1
Wanted / Re: EP128 power supply
« on: 2020.November.15. 21:09:24 »
I used a Spectrum+ power supply for a while and I can confirm it was the right polarity. Although the voltage seemed a little higher than the Enterprise one.

Overall, I wouldn't recommend it. A switching PSU like Elmer suggests would give a more stable supply. I use something similar to that now.

2
Hardware / Re: Capacitors - wrong orientation?
« on: 2020.November.09. 22:27:48 »
One note: rare fault, but if the L1 are broken then the TR2 will dead again, and again... (I about after 5 transistors found the problem at L1...)

Thanks for the tip.  I wound a new L1 myself so hopefully that will be okay.

3
Hardware / Re: Capacitors - wrong orientation?
« on: 2020.November.08. 23:04:29 »
Huge thanks to Wolfgang for starting this thread and to everyone else for the comments. A while ago, when I repaired my Enterprise 12V, I was following the schematic diagram rather than the PCB markings and this thread explains why I kept blowing transitors!!! :cry: 

It never occurred to me that the circuit diagram was wrong. I have now installed C9 with minus to the left. Fingers crossed this will work.

4
Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.October.19. 22:35:20 »
Amazing!!!!

5
Interface / Re: Internal memory expansion
« on: 2020.October.19. 22:31:15 »
If you type (blind) TEXT 40 it will reset the screen without rebooting.

To avoid blind typing, by default you can press F5 for "TEXT" or even SHIFT F5  which will redisplay an existing text screen.

I think this is a bug in EXDOS :oops:

I'm not sure it's a bug as such. EXDOS has no easy way of knowing what was previously displayed.

6
Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.October.11. 23:27:16 »
Excellent stuff!!!

7
Hardware / Re: Capacitors - wrong orientation?
« on: 2020.October.10. 10:49:20 »
That is on an issue 4 motherboard, which unfortunately has 300ns video RAM, so I presumably won't be able to change to a 6MHz clock unless I replace those. :(

Often chips are faster than the official rating, so you might be lucky.

8
Programming / Re: Graphics Attribute Mode Example
« on: 2020.October.03. 20:29:41 »
Off topic: The Amstrad CPC is a totally graphic computer, it doesn't have a text mode nor a buffer, but can emulate it. There is a Rom function that returns the value of a character given certain coordinates. A workaround is used: the rows of bytes that are found on the coordinates(on text boundaries) are compared with all the ones on the character set until a match is found.

I think this is probably what the Spectrum does as well with the SCREEN$ command. The Spectrum display is not a text buffer either. It's an attribute-based graphical display.

9
Programming / Re: Graphics Attribute Mode Example
« on: 2020.October.03. 13:07:26 »
They cannot be overwritten by space characters.

Actually, it seems that in ATTRIBUTE mode, you can overwrite by printing with space characters. Although that doesn't work in the other graphics modes, only in attribute mode.

10
Other topics / Re: How can one switch between WP versions?
« on: 2020.September.29. 10:32:47 »
Great finding, i checked what is called, and a small correction CALL USR(62905,0) should be used instead

Aha - good point! I just looked at it again and you are absolutely right. Thanks for the correction.

11
Other topics / Re: How can one switch between WP versions?
« on: 2020.September.28. 23:41:28 »
How did you find out the number 62907?

Years ago I think I worked it out by disassembling the EXOS 2.1 ROM. But more recently, I "rediscovered" it by using the built-in debugger in the excellent EP128emu.

12
Other topics / Re: How can one switch between WP versions?
« on: 2020.September.28. 10:39:46 »
I think that 2.6 was designed to replace 2.1 so you can't actually call it with an EXOS command. 2.6 does everything the original does so there's really no reason to use the original.

However the code is still there in the ROM so you can always call it directly if you want. For example, from BASIC...

Code: [Select]
CALL USR(62907,0)

13
Programming / Re: EXOS source code?
« on: 2020.September.28. 10:32:34 »
Did anyone ever produce an annotated disassembly of the EXOS 2.x ROM?

I have a partial disassembly (in English) that I made for fun a few years ago. It's probably 25% done. I worked out where the main bits were - reset code, WP, device drivers, BASIC functions etc. (The EXOS ROM actually contains some of the code for BASIC!) But I didn't get around to sorting out all the data or annotating everything. Unfortunately I don't have access to it at the moment, but I'll try to get hold of it and tidy it up so it's useful to someone else.

I also believe that the community has the original source code somewhere - part of the stuff from Werner Lindner (technical director of ENTERPRISE Computers GmbH). Is that right?


There's a neat disassembler toolkit for the Spectrum world (https://github.com/skoolkid/skoolkit) that uses profiling in an emulator to work out what is code and what is data. Do similar tools exist for the Enterprise?

Not as sophisticated as emulation, but several modern Z80 disassemblers will try to sort the code from the data automatically. In fact, I seem to remember that the EXOS file analyzer - http://epbas.lgb.hu/ - works out which is code and data.

14
Interface / Re: Internal memory expansion
« on: 2020.September.16. 10:34:15 »
Unfortunately, I was too optimistic about EXP2. I can close the top, but it bends the plastic out about 1mm.

Yes - I found that out the hard way too :(

Btw., I was not able to use a standard double-row header on EXP1. It seems the distance between the two rows is off. I used two single rows instead.

I had forgotten this, but I remember having a slight problem too! I seem to recall that the official boards in the EP128 are directly attached by 28 individual tall pins, so for them the off-spacing wasn't a problem.

15
Hardware / Re: Enterprise Deployment Attempt Over FPGA.
« on: 2020.September.12. 11:19:17 »
Well I just wired the VSYNC interrupts directly to the INT signal of the CPU, but I guess it's not correct. I'm not sure about how interrupts work in general. I have read about Dave's registers, but I am not sure how they work. For example, what is connected to INT1 or INT2?

On the Enterprise, interrupts are connected to the DAVE chip and then DAVE controls the INT signal of the CPU. Interrupts are latched by DAVE so they can get passed to the CPU (eventually) even if they occur when Z80 interrupts are temporarily disabled.

DAVE has 4 sources of interrupts...

1. Variable frequency interrupt - either 50Hz, 1kHz or a variable frequency specified by the tone generator (ie the pitch of sound)
2. An interrupt at 1Hz
3. INT1 - this is connected to the Nick chip interrupt
4. INT2 - I think this is connected to the network port, so you probably don't need to worry about it.

You can find out what interrupts have occurred by reading DAVE register $B4.
You enable/disable the different interrupt sources and clear interrupt latches by writing to DAVE register $B4.

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