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Topic: 4 bit vs 8 bit shift register help ? (Read 5734 times) previous topic - next topic

fungus


I think the 594 and 595 are close enough that you won't have any problems.


I think they're just different enough to cause problems.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Grumpy_Mike

Quote
so what is the difference between these 2 ICs

One has a tristate output and the other does not.

Please look at the data sheets for the two devices.

firashelou

i am looking but the thing is i can't understand everything but i would love to learn how to understand the whole thing or most of it .
thank you guys will see what i can do about it
Aiming for the unreachable !

Grumpy_Mike

All the data sheets are written in a different style. Look at the same maker for the two data sheets. The NXP has a pin description in section 6.
Look at the pin number changes.
On the 594 you do not need the SHR and the STR so wire them high.
SHCP is the clock signal
STCP is the latch signal

Tom Carpenter



I think they're just different enough to cause problems.



The only difference is one has a tristate buffer. If the OE enable pin is not needed, which it isn't, then the two are identical. Both have an output latch. Both have the same structure if you look at the datasheet:

Fig 4. page 3 : http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf
Fig 4. page 3 : http://www.nxp.com/documents/data_sheet/74HC_HCT594.pdf

Sure some pins have different names, but they have the same function:

74HC595:

DS = Data In
SHCP = Shift Clock In
!MR = Tie to VDD
STCP = Latch Data
!OE = Tie to VSS
Q0-Q7 = 8 outputs.


74HC594:

DS = Data In
SHCP = Shift Clock In
!SHR = Tie to VDD
STCP = Latch Data
!STR = Tie to VDD
Q0-Q7 = 8 outputs.





In that setup, where is the difference? They will not cause any flickering as both have an additional output register.
~Tom~

firashelou




I think they're just different enough to cause problems.



The only difference is one has a tristate buffer. If the OE enable pin is not needed, which it isn't, then the two are identical. Both have an output latch. Both have the same structure if you look at the datasheet:

Fig 4. page 3 : http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf
Fig 4. page 3 : http://www.nxp.com/documents/data_sheet/74HC_HCT594.pdf

Sure some pins have different names, but they have the same function:

74HC595:

DS = Data In
SHCP = Shift Clock In
!MR = Tie to VDD
STCP = Latch Data
!OE = Tie to VSS
Q0-Q7 = 8 outputs.


74HC594:

DS = Data In
SHCP = Shift Clock In
!SHR = Tie to VDD
STCP = Latch Data
!STR = Tie to VDD
Q0-Q7 = 8 outputs.





In that setup, where is the difference? They will not cause any flickering as both have an additional output register.


great explanation Tom that's what i needed then i am gonna try it the way you said it for the 594 and we'll see what will happen
Aiming for the unreachable !

fungus


Sure some pins have different names, but they have the same function:


I think that's what's confusing me - the names are all mixed up.

Yep, ignore what I said. It should work.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

firashelou



Sure some pins have different names, but they have the same function:


I think that's what's confusing me - the names are all mixed up.

Yep, ignore what I said. It should work.



ok thanks anyway for helping :)
Aiming for the unreachable !

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