Author Topic: Is there a better logic part for this than CD74HC73E  (Read 1049 times)

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Offline alank2Topic starter

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Is there a better logic part for this than CD74HC73E
« on: March 08, 2019, 05:21:43 pm »
I want to automatically assert the /WAIT line on a Z80 when it asserts the /IORQ line.  I only want it to assert on the high to low TRANSITION of /IORQ - I want to be able to reset it and release the /WAIT even while /IORQ may still be low.  Is there a better, more common part to use than CD74HC73E, preferrably in AHC ?
 

Offline T3sl4co1l

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Re: Is there a better logic part for this than CD74HC73E
« Reply #1 on: March 08, 2019, 06:50:02 pm »
Invert IORQ into type D ('74)'s CLK, D = 0, CLR = 1, PRE = release wait?

D f/fs are pretty standard, always been my impression that JKs are archaic?

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Online Benta

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Re: Is there a better logic part for this than CD74HC73E
« Reply #2 on: March 08, 2019, 07:32:45 pm »

D f/fs are pretty standard, always been my impression that JKs are archaic?


Certainly not!
The JK FF is one of the most powerful logic building blocks available.
If you have JK-FFs and D-FFs (plus gates of course) in your toolbox, you can do everything. Really everything.
But you do need both.
 

Online SiliconWizard

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Re: Is there a better logic part for this than CD74HC73E
« Reply #3 on: March 08, 2019, 07:40:16 pm »
Off the top of my head, it should be possible to achieve the same with (clever use) of a 74AHC123, which are readily available (whereas the 73 is not). To be checked though.

 
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Online Benta

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Re: Is there a better logic part for this than CD74HC73E
« Reply #4 on: March 08, 2019, 07:43:37 pm »
How on earth could a monostable multivibrator replace a JK FF?

 

Online SiliconWizard

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Re: Is there a better logic part for this than CD74HC73E
« Reply #5 on: March 08, 2019, 08:14:16 pm »
With the following arrangement maybe?

/IORQ line to pin /A
pull-up to pin B
pull-down to pin REXT/CEXT
(signal to reset output) to pin /RD
/WAIT line to pin /Q

 

Online Benta

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Re: Is there a better logic part for this than CD74HC73E
« Reply #6 on: March 08, 2019, 08:18:26 pm »
With the following arrangement maybe?

/IORQ line to pin /A
pull-up to pin B
pull-down to pin REXT/CEXT
(signal to reset output) to pin /RD
/WAIT line to pin /Q

Love it! Asynchronous design like in the ยด70s  |O

/sarcasm.
 


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