I found how to use one specific register bank for a function (interupt)by specifying using My_Bank and so, be faster (less PUSH and POP)but I would like to know if I can specify a variable to be located in one register bank (for speed), and, if yes, how to do it?
I see what you mean. For tight and fast ISRs keeping persistent variables in registers of a separate bank can speed things up. My guess is there is no way to do this in C. You'll have to use assembler for this.