[sebhc] My H8 Systems

Carroll Waddell CarrollWaddell at sc.rr.com
Tue Jun 1 15:01:31 CDT 2004


Dwight K. Elvey wrote:

>Hi All
> Well, I got my H8 with the Z80 running. All worked fine.
>I checked out my bootstrap and image transfer program
>( H89LDR ) and it works fine. I sent a copy to Steven so
>hopefully he gets it post to the web soon.
> I started on bring up my other H8 with the 8080 processor.
>This one had seen a lot of time stored someplace where
>the humidity was a little high. Many of the chips had
>the silver plated pin. This is a bad idea for chips in
>the long term. Any little crack in the plating and
>electrolysis erodes the pins from the inside out.
> Anyway, I spent many hours tracking down failures
>in the RAMs and other chips caused by pins that looked
>intact but were really broken inside. I plugged in one
>of the disk controller cards and used that to run its
>RAM test ( Not a really great test but it found most
>all of the problems, more about that later in my story ).
>Some of the failures were really tricky. I found that
>it is best to move possible failing parts to the lower
>order bits to save testing time. It didn't seem like
>I was ever going to get things working and I was beginning
>to run low on spare 4K RAMs. I spent more than 8 hours
>getting these to work.
> For those that are doing this, you need to have working
>RAM for both the beginning and the end of memory.
>It is hard to make sure all is OK when you are trying
>to test. I found that it is best to have just one
>working memory card at the 040.000 location and then
>leave a gap between that card and the one your testing.
>I would then modify the HL and DE registers from
>the ones set by starting at 030.003. It takes a little
>longer but some times one has to do what one can.
>This kept the monitor happy and allowed testing of
>really flaky boards that wuld otherwise have hung
>the monitor.
> In order to get the controller card working in the
>PAM8 environment, I had to undo the modifications done
>to make it work with the XCON8. This included removing
>a jumper and installing a 68 ohm resistor along with
>a 47 pf capacitor. Luckily, this board had both the
>ROM and the two RAMs still installed. The other board I
>have, that I use with my Z80 machine, doesn't have these
> The RAM test that they have could be improved. Instead
>of just incrementing the value, they could have use
>a rotate or a lfsr to create the values. It would
>significantly reduce the amount of time to test the
>RAM. A full 64K system take over 10 minutes to test.
>I recommend that if you are running this test that
>you watch the BC register from the panel. It needs to
>make a complete cycle from 000 to 377 before it had
>made a complete pass through your memory. The MSB's
>take for ever to get to. This is why I recommend moving
>suspect RAMs to the LSB's. This only takes a few moments.
> Another thing that the test doesn't do it that it uses
>the write/read type of test. It should be expanded to
>to a read/write/read. It wouldn't take much to modify
>since the C register isn't being used and that can
>hold the previous value.
> Well, on to getting the system up and running. I plugged
>my disk drive onto the system and things were looking much
>better. The only problem was that the serial input wasn't
>working correctly ( this is through the H8-5 board ).
>I would get the <BOOT> message fine from the booting
>disk but no matter what I typed, it would not continue.
>It took me a while to realize that it had to be something
>between the serial chip and the RS323 connector. A little
>time with the scope and I realized that the optical
>isolator was a little too slow. I swapped this with
>the one used for transmit ( I isn't pushed quite as much
>for the transmit side and can tolerate a little less )
>and finally got things working.
> It was late so I didn't get a chance to play with my
>H89LDR code and the H8-5 board. In any case, I now have
>two H8's up and running. Yaaaayy!!
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