memory bank in PIC16f877a

[PA3040]

Dear All
Please kindly help me to learn about memory bank in PIC16f877a
Please see picture in the attached
I found in the memory bank which is called ACCESSES AREA in addition to GPR and SFR register area
I sow this in Mid-Range MCU Family Reference Manual as Mapped in Bank0
Please advice

 

[wp100]

Hi,


( sorry - me again :-D)
First, the register map you are showing is for the 873A chip which just has 192 bytes of ram spead over Banks 0 and 1.
Banks 2 and 3 do not exist, but I believe, without checking, that if you set your code to Bank2 it will just reflect Bank0, and Bank 3 as Bank 1.

What is more interesting for you with the 877A chip is the 16 bytes of Access Areas in Banks1,2,and 3. 0x70 to 0x7F.

Anything you enter in this area is common to all banks 0 -3 , so it can be very handy to have those registers available without having to leave your current bank. Its something you will appreciate more when you write a large program that uses a lot of registers.
The area is often used for the contex saving registers used by the Interrupt routine