Trouble-shooting (another) old kitchen timer I wasted some time until realising there was some ambiguity about the pin layout of its CMOS
4020. Most sources show the first output as 'Q1' but others (including the one on which I based my ancient notes) apparently call it Q0.Is there a standard? Has it changed in the last 30 years or so?
Terry, East Grinstead, UK
Forgot to add my example link:
Terry, East Grinstead, UK
Where's Q2?
Bye Jack
The numerical siffix is *normally* taken to represent the binary weighting factor, as in '0' = 2**0 = 1, '1' = 2**1 = 2 etc etc. However this is not cast in stone, and some manufacturers have used the suffix '1' as being the least significant bit. As a point of note - Texas Instruments (TI) in the early 1970's actually used the lowest numerical suffix (0) to denote the most significant bit on the basis that this had the binary weighting of half full scale, the next bit (1) would represent a quarter full scale etc etc. This then made the least signicant bit suffix change depending on the total number of bits in the variable. Fortunatly they changed back to normality in the early 1980's. The TI 16 bit processor 9900 had this fun bit numbering system which caused a lot of pain in the early stages of of a product development where you were interfacing two different devices with different bit numbering schemes!
Andy
Q2 only available on 4040... seems the picture for your 4020 is wrong. Check here
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Thanks Andy, appreciate that full and clear explanation.
Terry, East Grinstead, UK
The 4020 has no divide by 4 or 8 outputs. So they will be labelled either Q0, Q3, Q4 ... to Q13 (/16384), or Q1, Q4, Q5 ... to Q14, depending on your source.
Terry, East Grinstead, UK
Some of those datasheets, like the one from TI, are partial reprints of the old RCA datasheets which are pushing 50 years old or more, before there wa s any accepted convention. The modern designation for a 14-stage would be Q
0-Q13. You can label them anything you like. Q1-Q14 is fine too.ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.