New uKIM; rev.1 board rework?

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New uKIM; rev.1 board rework?

Postby sr » Dec Thu 20, 2007 1:16 am

First of all, hello, Micro-KIM owners and discussers! I have recently assembled my uKIM kit. The smoke-test went well, and I will post a link to some photos as soon as I get the RS-232 interface tested and get the thing suitably mounted on a chassis.

I am having a bit of trouble with the rework instructions at brielcomputers, though, and would like to request some help. The rework instructions specify one rewiring that is now a part of the rev.1 board, and three others that are not. My uKIM is a rev.1. With the kit unmodified, I can write and read addresses that live on the 32K expansion board, but can not access anything at or above 0xf400 (no idea about the RS-232 function, as I still have to pick up the cable for this). The KIM-1 memory map shows nothing reserved in the upper 32K, so I assume that everything out to 0xffff should be writable.

I checked the rework instructions online, and the pattern of traces shown in the photographs does not seem to match the traces in the corresponding areas of my board. I notice that the board in the online pics has some sort of rough serial number painted on it, unlike my board, and speculate that the rework instructions are for the rev.0 board, and are different in rev.1.

I can try to trace PC traces and figure out where what is supposed to go (looks like address decoding logic, so nothing too complicated), but thought I'd ask on the board before plunging into things, especially since I've installed the IC sockets and ICs, and these obscure the traces. I am good enough with a soldering iron to get the uKIM together (obviously), but am a software guy, so will gladly listen to the advice of more experienced hardware hackers.

Thanks.
sr
 
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Postby vbriel » Dec Thu 20, 2007 8:40 am

Do not do the bugfix on the rev 1 board. The instructions are stated for the rev 0 boards. Rev 1 boards already have the fix installed.

Make sure the jumper next to the RAM card JP1 is removed for the 32K card. The ram card handles all the decoding when installed, the jumper gives control to the card.

Vince
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Postby vbriel » Dec Thu 20, 2007 8:44 am

Also,

I dropped the serial numbering after the rev 0 boards. It was too much trouble to do and have them come out correctly.

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Postby sr » Dec Thu 20, 2007 11:55 am

vbriel wrote:Do not do the bugfix on the rev 1 board. The instructions are stated for the rev 0 boards. Rev 1 boards already have the fix installed.

Make sure the jumper next to the RAM card JP1 is removed for the 32K card. The ram card handles all the decoding when installed, the jumper gives control to the card.

Vince


I see. The RAM card jumper is off, of course. If the rev.1 board does not require rework, I am left wondering why I can't write above 0xf400.

Hm... actually, had a look at http://www.brielcomputers.com/micro-KIM.html#ram, which says that the RAM card decodes 0x2000--0x9fff, and now I wonder why I am able to write below 0xf3ff. The KIM-1 User's Manual says that unused RAM begins at 0x2000 (sorry, I assumed that the 32K expansion lived in the upper 32K---but back in the day, you wouldn't just run the HO bit on the address bus to CE on the 32K SRAM, because there was no such thing as a 32K SRAM!), so I'm guessing that I'm seeing some wrap-around.

Anyway, I should get that serial cable and find a place on my working surface for my Linux laptop, so I can do more than just random fingerpoken. More posts to the forums, with original contributions rather than requests for advice, once I'm up.
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Postby vbriel » Dec Thu 20, 2007 3:04 pm

Yeah, sorry, I just posted my note in a hurry this morning. The RAM card decodes 0000-1FFF and gets that info from the Micro-KIM. 2000-9FFF is the 32K chip. Between A000 and DFFF is nothing. E000-FFFF is a shadow image of 0000-1FFF. So, whatever you write to 0 is also the same in E000. F400 is actually 1400-16FF set as a void memory area, not used.

More memory paging info is available on page 28 of the Micro-KIM manual.

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