[time-nuts] Rom Expansion for HP5370B

Bob Camp lists at rtty.us
Sun Feb 20 21:20:07 UTC 2011


Is the CPU strictly an I/O machine or does it do any of the timing for the 
counter?

If it's just I/O then indeed, replacing it would be a reasonable task.

-----Original Message----- 
From: Poul-Henning Kamp
Sent: Sunday, February 20, 2011 3:21 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Rom Expansion for HP5370B

In message <AANLkTi=Z8oX4dQWY_nRQDcnkMDHZRRc3QhsaB0=7_gZ+ at mail.gmail.com>, 
paul
swed writes:

>Though only 8K of eprom I suspect its cleverly coded.

It's not really that bad.  There has clearly been somebody there to pound
structure into the result, and there is very little evidence of 
code-bumming.

>So its quite speedy and does also have interrupt capability. At a cost of
>$3-4 each its nothing to use several for different apps like the front 
>panel
>display and keys, control for actual counting and finally a third for
>ethernet or GPIB. (Maybe I will get to that one day)

Well, all the existing I/O shares the same 16A8D databus, and there
is hardly anything gained from having multiple processors fight for
that bus.

The I/O is also very much built to reduce CPU work, the display/leds
are self refreshing, the GPIB has its own ROM based state-machine etc.

>But really the key to any of this would be the accurate decoding of the
>existing software.

I have 303 bytes undecoded right now, 256 of these is a table which
I suspect is related to floating point squareroots, and a fair
number of the rest are padding.  As I said it is quite structured.

It is a total no-brainer if you executed it by emulating a
M6800, and only intercepted a few places to add features.

>Though HP service docs are somewhat useful in this approach for the 5370
>vintage. At least you tend to be able to understand what IO does what.

The HP5370B is actually very good in that respect, I have been able to
figure out all the I/O that way.

>For me since the 3 5370s are working, I won't be hacking them anytime soon.
>Like'em the way they are.

Now, that's the other part:  It is a very good instrument.

The only feature I have been able to dream up yet is a digital
clock, and only because that is sort of the default for anything
with a display.

But it could be interesting to see what the hardware can do with
sufficient CPU resouces, because right now it is clearly CPU-limited.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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