>
>
> Well I've got to say it guys, this one has beaten me. I've gotta
move on. If anybody else gas managed to interface a 74165 to an OOPIC
by way of oSPIL drop me a line. For me, he wasn't possible, call it
what you will impatience, cowardice, ... I think there's an
incompatiblity there somewhere. Maybe it's just me!
> https://www.invite2messenger.net/im/?source=TXT_EML_WLH_InviteFriends
>
> [Non-text portions of this message have been removed]
>
Without a 74HC165, I can't test the code. But I can find a better
datasheet than I was using. The TI datasheet is here:
http://focus.ti.com/lit/ds/symlink/sn74hc165.pdf
It has a much better logic diagram and it has a discussion about CLK INH
QUOTE
Clocking is accomplished by a low-to-high transition of the clock
(CLK) input while SH/LD is held high and CLK
INH is held low. The functions of CLK and CLK INH are interchangeable.
Since a low CLK and a low-to-high
transition of CLK INH also accomplish clocking, CLK INH should be
changed to the high level only while CLK
is high. Parallel loading is inhibited when SH/LD is held high. While
SH/LD is low, the parallel inputs to the
register are enabled independently of the levels of the CLK, CLK INH,
or serial (SER) inputs.
END QUOTE
So, the code doesn't handle CLK INH properly. In fact, the best thing
to do is ground the pin and ignore it. The internal flops are clocked
by the logical OR of the CLK INH and CLK inputs. Only one is necessary.
The code also takes more time to execute when it handles CLK INH. But
the good news is that the IOLine can be used to trigger a logic
analyzer and serves to frame the transaction. Just don't connect it
to the '165. Lacking a logic analyzer, it is probably better to just
remove the object and code.
NOTE 3 on page 4 is also important. ALL INPUTS must be either logic 0
or logic 1, they can not be left floating. TI has an application
report that deals with this and I think it says the device will be
damaged due to excess current flow. Do you KNOW your '165 is working?
You can test it with your bit-banged code. That will also test your
electrical interface.
Next time I order something from Digikey, I'll add a couple of
74HC165's and see how it comes out. From the scope, I think it works.
Richard
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