Author Topic: Pin count difference - DM74S573N  (Read 1888 times)

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Offline bitmanTopic starter

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Pin count difference - DM74S573N
« on: February 18, 2018, 01:37:30 am »
What am I reading wrong here on the chip - I read this as a DM74S573N which I have the data-sheet for here http://pdf1.alldatasheet.com/datasheet-pdf/view/135427/NSC/DM74S573N.html. According to the data-sheet there should be 20 pins - but this chip only has 18?  Color me confused - but I guess I shouldn't be surprised?  I can find it listed on some sites for purchase as an 18pin chip - so I'm pretty sure I have the wrong data sheet, but this model is listed in the sheet and everything seems to match otherwise?
 

Offline bitmanTopic starter

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Re: Pin count difference - DM74S573N
« Reply #1 on: February 18, 2018, 01:47:20 am »
Hmmm - I found another datasheet that matches the chp http://www.datasheets360.com/pdf/4783000051525452916. Question from the newbie is, if the model number is the same, how does this happen? What am I missing when I look up the datasheet?
 

Offline Wimberleytech

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Re: Pin count difference - DM74S573N
« Reply #2 on: February 18, 2018, 02:26:27 am »
I looked in the 1977, 1980, and 1990 National databooks.  18 pins in all cases. I did find a 20-pin datasheet on the web.   :-//
 

Offline Jwillis

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Re: Pin count difference - DM74S573N
« Reply #3 on: February 18, 2018, 05:25:32 am »
 

Offline 2N3055

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Re: Pin count difference - DM74S573N
« Reply #4 on: February 18, 2018, 10:15:55 am »
74x573

18 pin one is old 4096-BIT TTL PROM by NS..
20 pin one is Octal D-type transparent latch; 3-state...

Yeah, there are many instances in industry when they used same numbers for different stuff...
 
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Offline Jwillis

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Re: Pin count difference - DM74S573N
« Reply #5 on: February 18, 2018, 03:53:08 pm »
Well that's odd, the block diagram in OPs datasheet is showing 16 connections.if you add the Vcc and ground that would make 18 .Its missing Q4,Q5,Q6 and Q7.
 

Offline glarsson

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Re: Pin count difference - DM74S573N
« Reply #6 on: February 18, 2018, 04:22:22 pm »
Well that's odd, the block diagram in OPs datasheet is showing 16 connections.if you add the Vcc and ground that would make 18 .Its missing Q4,Q5,Q6 and Q7.
Why is it odd that a 1k*4 PROM only has four data outputs (Q0 - Q3)? Why do you expect it to have Q4, Q5, Q6 and Q7?
 

Offline Jwillis

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Re: Pin count difference - DM74S573N
« Reply #7 on: February 18, 2018, 04:35:05 pm »
Well that's odd, the block diagram in OPs datasheet is showing 16 connections.if you add the Vcc and ground that would make 18 .Its missing Q4,Q5,Q6 and Q7.
Why is it odd that a 1k*4 PROM only has four data outputs (Q0 - Q3)? Why do you expect it to have Q4, Q5, Q6 and Q7?

Just that the pin outs are showing Q4-Q7 on pins 11,12,13,14
 

Offline glarsson

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Re: Pin count difference - DM74S573N
« Reply #8 on: February 18, 2018, 06:41:38 pm »
Just that the pin outs are showing Q4-Q7 on pins 11,12,13,14
But that pinout is for the 20-pin version that is not a PROM. The data sheet is about the 18-pin PROM, except the pinout on page 2.
 

Offline Jwillis

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Re: Pin count difference - DM74S573N
« Reply #9 on: February 18, 2018, 06:59:08 pm »
Don't get wrong.It's not my intention to argumentative.I was just wondering why they would present a data sheet like that.It just causes confusion.
 

Offline stj

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Re: Pin count difference - DM74S573N
« Reply #10 on: February 19, 2018, 08:39:11 am »
you are confusing a 74s573 with a 74ls573.
an easy mistake given that there used to be a schottky version of ttl called 74s, before low power schottky (74ls) was developed.

unfortunatly 74s was also used to designate bipolar rom by a couple of manufacturers.
not all, some used different prefixes to avoid this confusion.
 

Offline newbrain

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Re: Pin count difference - DM74S573N
« Reply #11 on: February 19, 2018, 03:59:44 pm »
Just that the pin outs are showing Q4-Q7 on pins 11,12,13,14
But that pinout is for the 20-pin version that is not a PROM. The data sheet is about the 18-pin PROM, except the pinout on page 2.
Actually, if look at the DS in the OP first post (but not in any other I could find online), you'll see that on page two a 20-pin pinout is shown.

That pinout, though, seems to be for a 512x8 bits memory (still 4096bits), such as maybe a DM54S472, so it has only 9 address lines but 8 data lines.
Probably an early, wrong, version of the datasheet.
Nandemo wa shiranai wa yo, shitteru koto dake.
 

Offline Jwillis

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Re: Pin count difference - DM74S573N
« Reply #12 on: February 20, 2018, 11:25:59 am »
Maybe my first reply was confusing but here is the datasheet.
 

Offline newbrain

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Re: Pin count difference - DM74S573N
« Reply #13 on: February 20, 2018, 12:46:44 pm »
Maybe my first reply was confusing but here is the datasheet.
An here is the "funny" one with 20pins...which is of course wrong!
Nandemo wa shiranai wa yo, shitteru koto dake.
 


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