[time-nuts] Generating a solid PPS from 10Mhz source

EB4APL eb4apl at gmail.com
Sun Jan 17 12:41:04 UTC 2016


We are drifting from the original problem (dividing 10 MHz to 1 PPS) to 
general questions such as hardware vs software implementation, 
obsolescence of parts, program data retention and big program sizes for 
trivial tasks, all of them also interesting.

Well, returning to the main problem I just checked the original PPSDIV 
program source from TVB in order to remind me the size of the code:
360 lines of assembler text code including everything even blank lines.  
This accounts for 62 lines of text header with a detailed explanation of 
how the program works which even include the schematic drawn in 
character graphics and 302 lines of code including comments.  Pruning 
this code of comment and blank lines it leaves 182 lines of executable 
This is the original PPSDIV code made for a PIC with more I/O pins that 
divides the 10 MHz input to 9 simultaneous outputs from 100 KHz to .001 
Hz, all of them synchronous.
The smaller versions made for 8 pin chips has about  97 lines of 
assembler code including everything.  This accounts for 46 lines of text 
header and 51 lines of code including comments.  Pruning this code of 
comment and blank lines it leaves 31 lines of executable code (well, 
and  a little more since I have a subroutine missing).
For personal use you can stock a couple of PICs if you are  afraid of 
their availability in case of a future failure.


On 17/01/2016 a las 1:40, jimlux wrote:
> On 1/16/16 10:07 AM, Poul-Henning Kamp wrote:
>> --------
>> In message 
>> <20160116080037.13903406057 at ip-64-139-1-69.sjc.megapath.net>, Hal 
>> Murray writes:
>>> kb8tq at n1k.org said:
>>>> The astonishing part of this “new world” is that a very complex 
>>>> chip that is
>>>> made in high volume is cheaper than a handful of less popular (but 
>>>> far less
>>>> complex) chips.
>>> It would be interesting to see the die sizes.
>> Die size is not really an issue until they become big enough to 
>> impact overall yield.
>> And apropos:  I just used a LPC810, to do 5MHz to 1Hz for my HP5065A 
>> clock.  It almost
>> feels surreal to use a 32bit ARM CPU, even in a DIP8, for something 
>> so mundane...
> And how many thousand lines of code (including libraries, etc. that 
> may have been pulled in)?
> I had just this discussion yesterday at work with someone.   These 
> days, silicon (even going into space) is much cheaper than people. 
> Sure, you could optimize a hand crafted little routine in assembler. 
> Or, you could just load up RTEMS, compile your program, link in 
> newlib, etc., and have it working in a day.  If you've got 2 MByte of 
> memory, nobody cares whether you use 1kbyte or 50kbyte.
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