What PID's/ SID's/FID's are

[Ralph L. Fullenwider]

Hello everyone:

For those who are not familiar with codes, multiplexing or other forms of
reporting used in this day and age, I will attempt to bring to light a
little about these systems in the later Coaches.

The reporting codes and information are inputs and outputs much like on the
computer you are using for the Forum. And each code is simply an address of
where in a computer, the information is stored. So in order to get a
readout for that code, you have to have the input/output (I/O) schedule for
the addresses.

Though we see the codes reported in decimal (number) form, the actual
addresses are usually programmed in Hex or Octal or even machine coding,
then converted to binary and finally to numbers. In doing this, one wire
can be used to send a signal out on and to report back on several addresses
depending on the speed of the polling process.

The reason for the software, readers and so forth is to convert these
multiplexed addresses to a form that we can attach a number to and have a
readout of what code or instruction is in that address.

The codes are usually preset with a read out of what it is. Example: A
polling takes place sending out a question to a certain address, then if no
flags are set nothing comes back. But if an address, such as the DDEC
address for Low coolant is polled and a flag set, it sends back a number of
13. Then you look up the code on the map and it tells you, code 13 is
coolant level sensor low, add coolant and the flag goes off satisfied.

This is much simplified, to be sure, but the general idea comes across.
Easy huh? Hope this helps a little for those wondering what people are
talking about in some of the posts.

Safe travels,

Ralph and Charolette Fullenwider
84FC35
Ralph's RV Solutions, Duncan, Oklahoma