AB5 timer bit accum/7 ?

[freefifo]

Ran across this bit in an AB5 program the other day"T4:75.ACCUM/7".Can someone please tell me what the /7 is?
Thanks
freefifo

 

[Gerry]

That's bit 7 of the timer accumulator word which will toggle for every 128 ticks of the timer's time base (while the timer is timing, of course).

 

[freefifo]

accum bit7

Thanks for the reply Gerry
Where can I find documentation on using these bits?

 

[Ron Beaufort]

there’s no official documentation that I know of ... but this might help ... notice that when you count in binary:

the ZERO bit repeatedly goes: 0-1-0-1-0-1-0-1-0-1, etc.
the ONE bit repeatedly goes: 0-0-1-1-0-0-1-1-0-0-1-1, etc.
the TWO bit repeatedly goes: 0-0-0-0-1-1-1-1-0-0-0-0-1-1-1-1, etc.

in other words, each successively higher bit cycles off and on only half as fast as the preceding bit ...

the best way to learn more about this is to set up a TON timer with a preset of 32767 (the largest value possible) and a time base of 0.01 seconds ... condition the timer rung with an XIO instruction addressed to the timer’s own Done Bit ... this will automatically “reset” the timer each time it gets done (about once every 5.46 minutes) then the timer will just start over again ... now try using different bits in the timer’s accumulator to flash the LED on an unused output ... notice that each time you move up to the next higher bit, the flashing action is only half as fast ... hint: watch the flashing action on an actual LED and not on the RSLogix display screen ... usually the screen update is not fast enough to determine exactly what’s going on ...

a note for any SLC-500 readers ... the SLC processor’s “free running clock” located at S:4 uses this same effect ... you can use the bits in this word as a “built-in” flasher mechanism without having to set up the TON timer rung ... sorry, the PLC-5 processor does not have this built-in “free running clock” ...

another note for the PLC-5 readers ... play around with the “flashing action” of the bits in word S:23 ... this is the “Seconds” word of the PLC’s built in "real time" clock ... using S:23/0 gives one second ON ... one second OFF ... one second ON ... one second OFF ...

using S:23/1 gives two seconds ON ... two seconds OFF ... two seconds ON ... two seconds OFF ...

but notice what happens when you move up too far ... since the “Seconds” value only goes up to 59 and then starts over at 0, the pattern gets messed up for the higher value bits ...

if you SLC-500 people want to try this “Seconds” word game, you’ll neeed to have at least an SLC-5/03 processor since the lower models don’t have a “real time” clock ... but they do have the “free running clock” at S:4 which is not the same thing ... also note that the “Seconds” value in the SLC processors is located at word S:42 ... not at S:23 ...

so many bits ... so little time ...

 

[freefifo]

Thanks Ron!

Thanks for the great reply Ron!