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Post by designcraft on Mar 2, 2016 17:47:03 GMT
First of all: Hello to everyone!  I'am a proud owner of a C128 DCR for a few days now, and i have a strange drive problem i think. When in C64 mode i tested it like this: open 15,8,15,"u0>m1":close15 load"$",8 list the list show the correct free bytes, both the floppy sides are visible. And i can format a floppy with: open15,8,15,"n0:dsk,10":close15 Formatting the disk is fast, and correct free bytes shown after that. I can save, load, etc all works. In c128 mode, when i insert the disk, and type "directory", nothing happens, the prompt just shows "ready" If i try to "header", or format with open15,8... the drive and c128 locks When I try to list the disk content with load"$",8 than the prompt shows "File not found" error. So everything works as it should in C64 mode, but nothing in C128 mode. Is the drive using other roms for the two mode, or whats the problem here? C128 basic rom, kernal rom? How to test, or debug it? Unfortunately i can't swap roms because i just have one 128. Thanks very much for any help in advance... |
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Post by Dragget on Mar 2, 2016 21:24:14 GMT
In reply to your question on my thread: My problem was different: the 128D would hang when I turned it on and the READY prompt would never appear. I fixed it by replacing the 2048wordx8 CMOS SRAM at C103 with a compatible IC. For troubleshooting, I used a guide I found at personalpages.tds.net/~rcarlsen/cbm.html. Here is a pic I took of the motherboard showing the area where the IC I replaced is located. The one I repaired is at the bottom just right of the socketed chip with "PCB ASSY" printed on the board under it.  Of course, as you can see from my current thread, now I have a different problem that I'm finding much harder to nail down.  |
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Post by designcraft on Mar 2, 2016 22:33:52 GMT
Strange, but mine is doing the same sometimes in c128 mode, so no ready prompt after the copyright text on top of the screen when the machine started...
Are you tested yours in C64 mode? If yes, what happened there?
I don't understand this c64 OK, C128 fault issue...
thank you!
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Post by Dragget on Mar 3, 2016 11:02:48 GMT
Strange, but mine is doing the same sometimes in c128 mode, so no ready prompt after the copyright text on top of the screen when the machine started... Are you tested yours in C64 mode? If yes, what happened there? It never occurred to me to test it in C64 mode, so IDK if the problem was happening there or not, but I suspect so, since the SRAM that was bad is used for the disk drive in both modes. |
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Post by designcraft on Mar 3, 2016 19:37:57 GMT
Yes, so I suspect the c128 ROM, because in c64 mode everything is working. The only one chip what is different is the rom, the floppy ic's are the same too in both modes. Or not?...
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Post by hydrophilic on Mar 4, 2016 12:23:10 GMT
The ROM? Interesting theory! (I never would have thought of that!) Well the nice thing is ROMs are easy to swap, so a simple test!!
[Edit]
Almost forgot... what is the function of the SRAM chip? I guess it is the RAM for the 1571 ($0000~07FF)?
I never owned DCR, so I am clueless!
[/Edit]
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Post by designcraft on Mar 6, 2016 21:32:33 GMT
I built a ROM reader with an Arduino and read the 318077-01 rom, and compared to the BIN file of the same rom downloaded from internet.
This rom layout is: C64 BASIC, C64 KERNAL, C128 editor, Z80 BIOS and C128 KERNAL.
So far so good, my rom is OK, every byte matches.
But the c128 basic is in another rom, so i will check that, and the drive rom's too...
"hopefully" i will find some mismatch. I don't think any other way that is made the drive works in C64 but not in C128...
Any idea?
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Post by designcraft on Mar 7, 2016 10:19:29 GMT
Read all the ROMs, C128 Basic and 1571 dos rom, and all is identical to downloaded .bin files...
So, I don't understand. PLA, or SRAM? These are all vulnerable, so maybe these are the next,
but i don't understand how this cause the working drive in C64 mode...
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Post by donno128 on Mar 14, 2016 16:41:14 GMT
The other thing different is burst mode is not enabled in 64 mode.
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Post by designcraft on Mar 15, 2016 23:56:19 GMT
Wow, thanks donno128, this is really interesting... Maybe that's the problem.
The burst mode serial function is in the MOS 5710 IC which is a gate array... combined floppy controller, and CIA.
from the wiki:
"Commodore embedded reduced (just 4 registers) CIA-like logic for the cost reduced Commodore 1571 inside the C128DCR (See Commodore 128) in a gate array called 5710 which also contains other functions. The 5710 CIA has the serial clock for the fast serial interface hardwired to a CIA6526 equivalent Timer A value of 5, leading to a per-bit time of 5µs on transmission. This is different from what used to be a Timer A value of 6 in the 6526 CIA in the original Commodore 1571. The 5710 CIA does not contain timer or timer control registers. It only contains two port registers and the register to control the serial shifter and its event."
So, can I switch off the fast serial burst mode in a c128dcr, from software, or hardware? How can I test this theory?
Sadly I can't find any 5710 replacement chip on the market...
The problem is that now i can't use the drive in c128 mode with single sided (1541) mode for testing, i can't do "u0>m0", probably can't communicate with the drive because the wrong serial connection...
The serial comm speed is dependent from the 16MHz crystal, should I check out that too? The crystal is able to go wrong?
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