Z80 CLK DRV

2 Jul 2012

...

  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.  
 Is it not plausible that 330 ohms to ground represents 327 ohms to Vcc
 plus three ohms Vcc-to-GND? 
I would be suporised if this thing drew a steady 1.6A from the 5V line, 
which would imply that this '3 ohms' is not a fixed resistor. And most of 
the tiem (read : except for very odd cirucits), things draw less current 
when yoy measure their resistance with a DMM. 

Are htese reisstnace measurements essentially the same if you swap the 
probes round? 

Also, is this with the device on the PCB or removed? If the former, then I 
could well beleive that the 'resistance' between the supply lines was 3 
ohms...

-tony

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Z80 CLK DRV