I just found out that the simple instruction of dividing an 8 bit register by another, with an integer result and a remainder does not exist in the PCI16F1823...

Not that this will help you in the present instance, but this sort of thing is part of why I suggested a while back that you consider using the 16-bit PICs (dsPICs & PIC24F): the instruction set is much more capable, and makes assembly language programming a lot less painful.

I don't want to risk derailing the thread, so I'll shut up now.

 

Not that this will help you in the present instance, but this sort of thing is part of why I suggested a while back that you consider using the 16-bit PICs (dsPICs & PIC24F): the instruction set is much more capable, and makes assembly language programming a lot less painful.

I don't want to risk derailing the thread, so I'll shut up now.

​

 

Dumb question, the PIC16F1823 manual states that the "SUBWF f, d" function does is "Subtract (2's complement method) W register from register f.

What does that mean exactly? That the numbers to be subtracted must have a 2's complement format, or that the result will be represented in 2's complement or something else?

 

As follows:
SUBWF
Subtract (2’s complement method)
W register from register ‘f’. If ‘d’ is
0, the result is stored in the W
register. If ‘d’ is 1, the result is
stored back in register ‘f’.
Not sure what debugger MPLB-X has but MPLAB-IDE has a few one such as MPLB SIM you can step through the pgm and see the results in any selected register etc.
Max.

 

That just describes the internal method. The instruction works on your "regular" bytes and subtracts W from F. You must supply the destination, which can be W or F. If W > F, STATUS,0 is clear. If W <= F, STATUS,0 is set (=1).

That causes some confusion with the way STATUS works during addition. Just think of it as the carry/borrow bit.

 

I understood as much. I was just wondering if say 255 - 127 = 128 ... or if the result would be something else because of that 2's complement thing...

 

See my late edit on MPLAB-SIM etc.
Max.

 

If w=127 and f=255, then subwf <regf> =128. You can put the answer in either f or w.

If you do multi-byte subtraction, you will want to use subwfb for the high byte as that avoids having to check STATUS,0.

 

If w=127 and f=255, then subwf <regf> =128. You canput the answer in either f or w.

thanks ... as I said, I do understand the instrucion. It's the 2's complement thing that got me a little confused.

 

Subtraction via 2's complement method means: complement (in 2's fashion) the subtrahend, and add the result to the minuend, resulting in the difference.

So, 2's complement subtraction is actually addition.

 

I have MPLAB loaded on my project page, if I want to see exactly what the result is on a certain register/instruction, I just single step through that section and see immediately what the result is.
Max.

 

Trying to learn how to use the debugger at this point. I can't figure out how to add watchers to my variables. I'm doing what the help instructions ask me to do (right click on the variable and select add watch) and it's just not working. All other registers report just fine, but when, say, I right click over DIVIDEND (which was declared as DIVIDEND EQU 075H) and select new watch, it'll take to a dialog box such as this one:

​

And after clicking ok, it just won't add it to the "Watches" list.

 

This is so freaking frustrating...

 

Trying to learn how to use the debugger at this point. I can't figure out how to add watchers to my variables. I'm doing what the help instructions ask me to do (right click on the variable and select add watch) and it's just not working. All other registers report just fine, but when, say, I right click over DIVIDEND (which was declared as DIVIDEND EQU 075H) and select new watch, it'll take to a dialog box such as this one:

View attachment 211581​

And after clicking ok, it just won't add it to the "Watches" list.

Ha! The very reason I still won't use MPLABX. You need to reserve your register "variables" as resources, otherwise, MPLABX just doesn't understand.

In the olden days, one could "view" a named address any way they wanted to. But those darn whipper-snapper millennial tool coders are too smart for that.

 

You need to reserve your register "variables" as resources

ok ... how am I supposed to do that?

 

I have played around the edges of MPLB-X using assembly, but so far it has been a frustrating experience.
I guess I am used to MPLAB v8.92 . Where my assembly experience has been so far.
I get the the distinct impression that Microchip has abandoned assembly support in favor of C , going by all their current app notes and examples etc.
Including MPLAB-X.
Max.

 

César, are you still using MPLAB 8.92?

 

César, are you still using MPLAB 8.92?

Nope ... I'm using MPLAB X 4.2, but now I'm uninstalling it and installing the most recent one, Which is X 5.4, I believe.

 

Don't do it.
Get 5.25.
Otherwise you will have to deal with the new Assembler. No the best now for you.

 

ok ... how am I supposed to do that?

Use the RES directive, not EQU when defining them. IIRC, you must use relocatable code.