74ls521

[dwuihf]

i study circuit and it has comparator(74LS521) with 8 pins binary input Q,P. by referring to the datasheet of 74LS521, P=Q  as output active low with NAND Gate. i have the the value of Q,but i e dont have it for P,so does it mean that both input value are equal to active this comparator??

[Tien_P]

Hi,

I don't know what a 74LS521 is, I can find a datasheet for it.  You may want to post your file, it helps us see what you are trying to do.

[dwuihf]

sir,

     74LS521 is identity comparator. referring to  to my circuit in attachment for 68k microprocessor.the comparator used to generate signal to enable secondary decoder 74LS138.this decodergives output address frompins Y3 and Y5. now my questions:

-how does the comparator generate out put signal?

-what is the address at output of decoder 74LS138 at  COMP,DAC_LED lines?

i have set input signal to one of the 8 bit input lines of 74ls521 as :00010001 from S0 to S7. what is the address at other 8 bit lines of the comparator?

thanks and appreciate for replay to my questions.