Assembly programming, how to add a 24-bit number: PIC Microcontroller?

Question by kevins963: Assembly programming, how to add a 24-bit number: PIC Microcontroller?
I’m trying to study for an exam for my embedded systems class and was hoping someone could go through this question and explain how it is done.

Here is the question: Show sequence of instudction to subtract 1 from a 24-bit signed integer value stored in data memory locations DATA_U:DATA_H:DATA_L. Assume that these memory location are located in Access RAM.

Also, could someone explain the difference between Access and Banked RAM.

We are using the Pic Microcontroller 18F452
Thanks for you help

Best answer:

Answer by Kasey C
Well, here’s a couple hints:

1) Substraction: do it one byte at a time, then carry over, if need be.

2) Access RAM basically means you only get access to maximum of 8-bit worth of RAM. Banked ram allows you to switch banks, thereby adding RAM capacity.

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