looking for TTL latch IC

[exxos]

---
It's a link to the schematic I posted on
alt.binaries.schematics.electronic.

If your ISP doesn't carry abse let me know and I'll email it to the
email address you've posted here, otherwise email me with your real
email address and I'll email it to you there.

I cant see it working, the OR input, fair enough, if any inputs go high then
theres a high output. On the output side, The inverted input Nor will always
end up as a high on U2D. It looks like it might work if 2 outputs such as D3
& D4 both go high, then the state of U2D would change. I've drawn out on
paper the states of the logic at each gate and I can't see that it would do
anything. ?

Chris

 

[exxos]

I've posted a new drawing on the same group as your pdf..

I think this is what you are doing.

It still uses 3 IC's like yours. Here the data comes in, passes via 2
tri-state buffers. The Latch clock input is take off a OR gate, so
basically when any input pulses high it will pulse the clock input. This
assumes however, that the 3state buffer is as slow as they come, since of
course, the clock input to the latch needs to pulse slightly faster than the
data lines to latch it. The output is ORed to the buffer enable so inputs
are off. The buffer also ensures the clock is not pulses again.

Actually, the OR gate with the ABCD inputs could be swapped with resistors,
then the delay of the second set of buffers should just be enough to ensure
the data is still on the latch when the clock goes low.

Chris

 

[John Fields]

I cant see it working, the OR input, fair enough, if any inputs go high then
theres a high output. On the output side, The inverted input Nor will always
end up as a high on U2D. It looks like it might work if 2 outputs such as D3
& D4 both go high, then the state of U2D would change. I've drawn out on
paper the states of the logic at each gate and I can't see that it would do
anything. ?

---
The gates on the outputs aren't inverted ORs, they're DeMorgan
equivalent ANDs.

The ANDs are HC08's, the ORs are HC32''s, and the latch is an HC175.

Upon asserting RESET-, all the true (Q) outputs on the 175 will go low
and all the complementary (\Q) outputs will go high. The highs on the
complementary outputs will propagate through the ANDS and will enable
the clock input of the 175.

If any data inputs (DIN1 - DIN4) are high when RESET is released, the
clock input will have already gone high when RESET was asserted and
the outputs will remain in their RESET state until ALL the data inputs
go low, then ANY of the inputs goes high again. When that happens,
the corresponding 175 input will go high and the clock will go high
three gate delays later, propagating the inputs which went high prior
to one setup time through the 175 to its true outputs and latching
them. When any of the 175's true outputs go high its corresponding
complementary output will go low, that low will propagate through the
ANDs and, three gate delays later, will cause the 175's clock input
to go, and stay, low.

If the 175's inputs are low when the 175 comes out of reset, the true
outputs will be low, the complementary outputs will be high, and the
clock will also be low. In this case, the first high data input will
appear on the corresponding 175 input and, three gate delays later,
will cause the clock input to go high, clocking that high through the
175 and latching it.

Data must stay high for three gate delays plus one setup time plus one
hold time to be considered valid.

If you need something better/faster, I've posted a new schematic for
you on abse. let's move it over there OK?

The ANDs are HC08's, the ORs are HC32's, the flip-flops are HC74's,
and you can get all of their AC characteristics by looking at their
data sheets.

 

[Tom Del Rosso]

In John Fields typed:

Since I took a couple of hours out of my life to come up with a
solution for you, for free, I'd like to know.

That's TWO dinners-for-two at the Rainbow Room, or the Palm Court, or
one of each. I prefer the Palm Court myself.

 

[Tom Del Rosso]

In Mjolinor typed:

Please explain this, I got a "new email" box up, (Microcrap SW)

Just copy the address into the browser. OE assumes it's an email
address, whereas other readers ask, but can't tell automatically if it's
mail or news. I think the OE way is actually better since I click email
links much more often. The problem is avoided if the link starts with
"to specify that it is a news link.

 

[exxos]

---
The gates on the outputs aren't inverted ORs, they're DeMorgan
equivalent ANDs.

The ANDs are HC08's, the ORs are HC32''s, and the latch is an HC175.

Upon asserting RESET-, all the true (Q) outputs on the 175 will go low
and all the complementary (\Q) outputs will go high. The highs on the
complementary outputs will propagate through the ANDS and will enable
the clock input of the 175.

If any data inputs (DIN1 - DIN4) are high when RESET is released, the
clock input will have already gone high when RESET was asserted and
the outputs will remain in their RESET state until ALL the data inputs
go low, then ANY of the inputs goes high again. When that happens,
the corresponding 175 input will go high and the clock will go high
three gate delays later, propagating the inputs which went high prior
to one setup time through the 175 to its true outputs and latching
them. When any of the 175's true outputs go high its corresponding
complementary output will go low, that low will propagate through the
ANDs and, three gate delays later, will cause the 175's clock input
to go, and stay, low.

If the 175's inputs are low when the 175 comes out of reset, the true
outputs will be low, the complementary outputs will be high, and the
clock will also be low. In this case, the first high data input will
appear on the corresponding 175 input and, three gate delays later,
will cause the clock input to go high, clocking that high through the
175 and latching it.

Data must stay high for three gate delays plus one setup time plus one
hold time to be considered valid.

If you need something better/faster, I've posted a new schematic for
you on abse. let's move it over there OK?

The ANDs are HC08's, the ORs are HC32's, the flip-flops are HC74's,
and you can get all of their AC characteristics by looking at their
data sheets.

Right, I will take the newer drawing since that one looks a lot easier to
read than the first one. It looks like you have added in a lot of reset
function which will of course help over my orig drawing.

The last part of the circuit hasn't been taken into account asyet. This is
the part where the outputs are feed back into the inputs.
Now assume I link all the Q's together via a 1K resitor and diode back onto
the inputs. I will add this onto your drawing for you to see. The last part
of the circuit will pull all 4 inputs high (to 12volts not 5v) upon any of
the outputs being latched on. I dont think this will effect your design
since the inputs should be disabled.

abse is very slow on pipex, I can access text groups fine, though abse takes
about 5mins just to DL a message, I will post the edited drawing on there,
though it maybe a while before it appears on there.......

thanks
Chris

 

[John Fields]

Right, I will take the newer drawing since that one looks a lot easier to
read than the first one. It looks like you have added in a lot of reset
function which will of course help over my orig drawing.

The last part of the circuit hasn't been taken into account asyet. This is
the part where the outputs are feed back into the inputs.
Now assume I link all the Q's together via a 1K resitor and diode back onto
the inputs. I will add this onto your drawing for you to see. The last part
of the circuit will pull all 4 inputs high (to 12volts not 5v) upon any of
the outputs being latched on. I dont think this will effect your design
since the inputs should be disabled.

---
Go to abse for the answer to your post and, if you don't mind, let's
move the discussion to abse since we're trading drawings. Since it
takes you a long time to download binaries from abse, if you'd like
to send me your real email address I'll email the schematics to you as
well as posting them to abse. If you choose not to, they'll be at
abse anyway. See ya there!

 

[exxos]

---
Go to abse for the answer to your post and, if you don't mind, let's
move the discussion to abse since we're trading drawings. Since it
takes you a long time to download binaries from abse, if you'd like
to send me your real email address I'll email the schematics to you as
well as posting them to abse. If you choose not to, they'll be at
abse anyway. See ya there!

ok ABSE it is, you can mail me at
tesla@@@@@@@@@@@@@@cps-electronicsREMOVE.co.uk

hopefully you can make sence of that, hopefully the spammers wont

Chris