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Subject: 74HC525 IC
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NNTP-Posting-Date: Thu, 07 Nov 2002 10:26:08 EST
Organization: OzEmail Ltd, Australia
Date: Thu, 7 Nov 2002 01:51:02 +1000
I purchased a Dick Smith Parallel Port Interface. It basically uses 3x
74HC525 and a TLC542. The 74525s are chained to form a 24bit shift
register. You place the 24bit data as follows.
enable the three 74525s
for i = 1 to 24
place a 0 or 1 at Pin 14
strobe pin 11
(during this strobe pin 9 will send a bit (0 or 1) to the next chip's
pin 14, etc)
after all the bits have been loaded, simply strobe the register clock pin 12
of each 74525
After all the tests and measurements, the first chip refuses to show
anything on Pin 9 and hence will not complete the shift to the next IC. I
have swap the 74525 with others, so unless they are all faulty, I have ruled
the chip out.
I have checked pin 10 which is tied to VCC and cap to gnd. I guarantee the
Pin 14 has the correct 0 or 1 state that I am sending.
Pin 16 has VCC and Pin Gnd
Pin 10 tied to VCC
Pin 11 strobes fine.
Pin strobes fine.
Pin 13 selects the chip by going low and works fine.
All above tested at the chips pins.
Any ideas or pointers to the right data for this chip. I have check google
Thanks in advance.
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