1 Jul
2012
1 Jul
'12
3:08 p.m.
On 07/01/2012 06:00 PM, Chuck Guzis wrote:
Unless there's an external pullup resistor, I can't imagine that this
is an OC output or that the drive is capacitively coupled Did you
try the diode (high voltage) setting on your ohmmeter?
I find that 330 ohms to ground part a bit odd. 327 ohms to Vcc is ok;
Zilog specs (if I recall correctly) a 330 ohm pullup on the clk line.
Z80s are very easy to design with, but their clock drive does require
just a bit of special attention. I'd think doing it with a
purpose-built hybrid is really a very expensive example of complete
overkill; worst case just pump it through a 2N3904 running OC with a 330
ohm pullup. Wouldn't you think?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
It should be fairly simple to verify. The input to
the clock driver
should show about 220 ohms to the Vcc connection and about 710 ohms
to the ground connection.
The Input is showing 330 Ohm to GND and 327 Ohm to VCC. The Output has
no measurable Ohm, neiter to VCC, nor to GND.