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simonwai999
Joined: 30 Jun 2008
Posts: 113
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 04 Jul 2008 19:51 Re: circuit analysis |
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hi guys
in the circuit as i can see
pic16f84 rb7 is connected to the middle IC 74hc374 pin 18 then
then this pair joins the pin 3,4,7,13,14,17,18 pins of the bottom IC 74hc374
Am I right? If not, please kindly correct me
Thanks a lot
Added after 1 minutes:
sorry here is the circuit
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laktronics
Joined: 06 Jan 2007
Posts: 808
Helped: 134
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| 05 Jul 2008 5:29 Re: circuit analysis |
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Hi,
No, it is a buss connection. RB0 to RB 7 respectively to be connected to D0 to D7 of each 374 IC.
Regards,
Laktronics
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simonwai999
Joined: 30 Jun 2008
Posts: 113
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| 05 Jul 2008 14:52 Re: circuit analysis |
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hi folks
i found this pixie circuit on the net
but i never used 74hc374
so i searched the net and found its datasheet
http://www.futurlec.com/74HC/74HC374.shtml
from what I know when clock control pin of this ic is low
and the clock input is high
if we send b '11111111' from Rb0-rb7 of the pic chip
the output of the two 74hc374 will be '11111111' too
and when the clock input is low
then all outputs of 74hc374 will hold 11111111 til the next high input from the pic clock
it is how this circuit works
the bottom q0 to q7 are connected to the led array cathode pins
and q0-q7 of the middle 74hc374 are connected to the led array anode pins
so it means when the clk input of the middle ic is high
if we send 11111111 to the d0-d7 of the ic it then sets all pins from d0-d7 all high
then when they are high , we then send a low clk input to the same ic
to hold all pins from q0-q7 high
and it comes to the bottom 74hc374
since rb7 , d7 ( in the middle ic) and d7( at the bottom ic) are connected
so when we set the mid ic do-d7 high
we set the bottom ic d0-d7 high too
that's not what we want
so now we send 00000000 do-d7 all low with its clk input high
now all leds in the array should light up
and if we change the input bits we can make diff patterns
folks
i am just guessing around
since i am not good at electronics
if i am incorrect, please enlighten me
Thanks so much in advance
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