- assuming the power supply is correct and clean,
Checked.
- you did put pull-up resistors on the 1802 inputs such as nDMAOUT and
nINTR, didn't you?
Done.
- check the Examine mode.
The idea is each push of the INPUT switch should result in a presentation
of the memory contents.
Assuming the memory contents is somewhat random at this point, the
display should present random values.
That's one of the problems. Even if I push the input button, *Q* output of
the the flipflop (4013) doesn't change. Seems like the 4013 doesn't work
properly.
I'm suggesting all this from just looking at the
schematic and 1802
datasheet, errors are possible and sanity checks will be a good idea.
I checked both 1802s. They work fine. Also, the damn 4016s does not
anything let through. I tested them (for the third time) on a separate
breadboard and they work fine. When I place them back, they stop letting
anything through. When I set any of the output pins (bus wires), the
display changes accordingly (for instance setting pin 2 of the 4016 will
set the display's content to '2' from '0'). It seems to me that the
fault
must be somewhere in the input circuitry. Will remove the 4013 and test it.
On 2012 Mar 9, at 5:29 AM, Gergely L?rincz wrote:
Brent, I checked the 1802 (both of them) and they seem to work fine. When
the CLEAR and WAIT pin are set high or low
accordingly, TPA and TPB sends
timing pulses (checked with the scope), the status pins SC1 and SC0 show
the state of the processor (checked it against the truth table, works
fine). I think they work fine. If you have any ideas how to test the 1802s
further, let me know!
Greg
On 8 March 2012 08:23, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
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://inco…
>
<h**ttp://incolor.inetnebr.com/**bill_r/elf/html/elf-1-35.htm<http://incolor.inetnebr.com/bill_r/elf/html/elf-1-35.htm>
> >
>
http://incolor.inetnebr.com/****bill_r/elf/html/elf-1-36.htm<http://inco…
>
<h**ttp://incolor.inetnebr.com/**bill_r/elf/html/elf-1-36.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.
>
>