Electronics Substituting the 74LS74N with the 74LS175

Would the the Preset pin on the 74LS74N be the Master Reset on the 74LS175.



I really know nothing about using ICs so Im just guessing.

 

Depends. I went looking for the 2 ICs listed and came up with varying results depending on manufacturer. A couple 74LS175 did not have MS at all.

Since there are varying manufacturers, check the data sheet for each device you listed. The master reset and the Preset do the same function, but make sure they are both ActiveLow.

Its a good chance they are the same.

 

Basically, Im wondering howto us that IC in this circuit:

 

Without going into tons of detail, I say yes. Just wire the MS the same as the PRE pin.

 

ok, what do I wire to where?

this is the pinout for the 74ls175:

 

This will work as 175 pin/74 pin.

9 - 3
1 - VCC (see below)
2 - 5
4 - 2

Looking at the schematic though, it seems that the circuit wouldn't work very well. I'm looking at the datasheet from Fairchild, and it says that if both PRE and CLR are both held low, then the outputs will go high no matter what, but a high transition for either or both will result in unpredictable outputs. The two should both be kept high so as not to hijack control from D/Clk inputs.

Going back to the original question, no, PRE on the 74 and MR on the 175 are not the quite same. The PRE, when set active (PRE, MR and CLR are all active low signals), throws Q high and Q' low. MR on the 175 is actually the same as the CLR on the 74, both set Q low and Q' high. The schem looks like you don't want to be able to independently control the outputs, so tie pins 1 and 16 (how convenient, they're right across from each other) so that MR stays high.

 

thanks whypick1,

You woudlnt be able to provide me with a schematic or anything would you?

 

nevermind, I got it working.

 

are there any other transistors I could use besides those huge IRF510s? Size is really an Issue here