On 2012 Mar 7, at 8:21 AM, Gergely L?rincz wrote:
I finally had time to have a look at the schematics. I
realised
that this
schematics replaced the two 4050's with 4049s. Can you confirm that it
works? Will purchase a couple of 4049 this week, wish I wasn't
under my
overdraft...
Inverting or non-inverting: it depends on other aspects of the
implementation.
Comparing with the schematic here:
http://incolor.inetnebr.com/bill_r/elf/html/elf-1-35.htm
http://incolor.inetnebr.com/bill_r/elf/html/elf-1-36.htm
(There is an error on page 36: IC5 at the RUN switch is labelled as
4050 (non-inverting and correct) but shown as an inverter.)
If you are following the original design strictly it looks like there
should be a 4049 and two 4050s.
The implementation I happen to have uses three 4049s because:
- simple LEDs are used for the display and so required inverters,
- the display latch is inverted as it is a different latch type,
- replaced the RUN-switch single-element non-inverting debounce
circuit
with a two-inverter circuit like the other debounce circuits.
I mentioned my schematic because it shows things on one page and the
control flow is clearer, I hope the implementation differences aren't
confusing things too much.
You mentioned checking a few things, but I don't think you actually
told use what the problem symptoms are.
Is the 1802 oscillator running?
One suggestion would be to check that the levels at the mode inputs
of the 1802 are correct for given switch settings.
On 6 March 2012 00:55, Gergely L?rincz <alkopop79
at gmail.com> wrote:
> Thanks for the schematics, amazing!
>
> On 5 March 2012 09:09, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
>
>> On 2012 Mar 2, at 6:08 PM, Gergely L?rincz wrote:
>>
>> I wonder if anyone has experience with Cosmac Elf. I've been
>> trying to
>>> build one on breadboard but have troubles with the input
>>> section. Please
>>> let me know if you have built one! Thanks
>>>
>>
>> I was refurbishing a school-project implementation from the 70's
>> (not
>> mine originally) just last summer.
>>
>>
http://www.cs.ubc.ca/~hilpert/**e/cosmacElf/index.html<http://
>>
www.cs.ubc.ca/~hilpert/e/cosmacElf/index.html>
>>
>> There's a re-organised version of the schematic there.
>>
>> I wasn't familiar with it in depth before this, although I
>> remember it
>> from the Pop Electronics article in the 70's. Kinda cute for its
>> simplicity.
>>
>
>