But, just to show the gaps in my knowledge, learning that the “h” told me to read FF and 0F as hexidecimal numbers was something I had long forgotten (if I ever knew it).

FFh and 0Fh are the states of the bits in the register. The “h” is telling us the “FF” or “0F” is in hexidecimal. Two hexidecimal numbers make means it is eight bits. I haven’t covered hexidecimal in a post, but it is couting with a base 16. So we count 0,1,2,3….9,A,B,C,D,E,F. You probably know this Whit from your other programming, maybe others don’t. So the FF can be decoded to binary as “11111111″ or 0F is 00001111.

It is imporant that the table on page 30 define each state if it is known or not known. When you are writing programs in SX/B or SASM or C you need to understand how the registers could get modified. You wouldn’t want to have your program store a value in a register that could get corrupted or assume a value exists in a register at startup after a reset condition occurs unless you are certain you know what that it can persist.

It is very important that your program defines registers and states and assume very little. A program will be more robust in this regard, but that is a whole other text book!

This is very good info. I think I actually got more out of pages 28 and 29 (meaning I understood more of what it was saying).

I have to ask some very basic questions about the chart on page 30. I understand that it is showing us the state of each register (like a little box with info in it) at each of the reset types (5 types in all). Some registers are FFh and some are 0Fh (is this low or high, 0 or 1, on or off - I assume so, but it is a guess). Some are undefined, meaning we might not know what the state is. Others are partially known and partially undefined. The condition of all is determined by the method of reset. Is that basically correct?

As regards page 30 (though I don’t understand many things), it looks like the variation in register states is very slight (although particular for each reset). I couldn’t really figure it out, but did notice that at power-on and brown out - more registers are undefined. This makes sense. Other resets (wake-up, watchdog timer, and MCLR either leave particular registers(the ones undefined in Power-on or brown out)in their current state or redefine them to a particular state. And therefore, at the power-on or brown out resets, some registers may have an undetermined state. This would mean (I think) that they would need to be set at a paticular state (in order to know for sure what was in them).

Am I even close?