control devices via parallel port, save state of each address?

sc2sc1 said:

hello,
i am trying to control devices via parallel port, in Attachment the circuit diagram, devices will be connect to 3 flip flops.

assume that i want to switch ON the first device in the first flip flop, so the [0 - 3] data bus = 1000 and decoder input = 01 then 00 to generate puls to the flip flop.

now if i want to switch ON the second device the [0-3] data bus = 1100 and so on.

is this the correct method?
is there any more efficient design?
thanks.

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Mikebits said:

Just make sure your data bits are valid before you output address to make clock. I also assume you will tie your enable pins and MR pins to the right logic level.

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ericgibbs said:

You should store an image of each of the states of the 175's in the PC memory
I would also use the Enable line on the 139.

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sc2sc1 said:

thank you for web site link, i will connect the pins correct
thank you, This is what I will do

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ericgibbs said:

hi,
Have a look at these files, they may help.

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