#2244 divuchar and moduchar access 0x7f didn't switch bank

[Athena Chuang]

I am working on an open source project, an IDE for SDCC. And emulator for mcs51/pic16/pic18.

Here is the github address:
https://github.com/athenajc/XideSDCC

I found divuchar and moduchar access 0x7f didn't switch bank.

Here is the sample code.

#include <pic16f628a.h>
void main(void)
{
    unsigned char i;
    for (i = 3; i < 16; i++)
    {
        PORTA = i % 3;
        PORTB = i / 3;
    }
}

__divuchar:
    0000D2  1283    bcf STATUS,5       <--- here had switch to bank 2
    0000D3  1703    bsf STATUS,6
    0000D4  00AC  movwf 0x2c    
    0000D5  087F   movf 0x7f,w         <--- STK00 is at 0x7f
    0000D6  00AD  movwf 0x2d
    0000D7  01AE   clrf 0x2e
    0000D8  3001  movlw 0x1
    0000D9  00AF  movwf 0x2f
    0000DA  082D   movf 0x2d,w
    0000DB  1D03  btfss STATUS,2
    0000DC  28DF   goto _00107_DS_
    0000DD  30FF  movlw 0xff
    0000DE  2902   goto _00115_DS_


_moduchar:
    0000B9  1283    bcf STATUS,5
    0000BA  1703    bsf STATUS,6
    0000BB  00AC  movwf 0x2c
    0000BC  087F   movf 0x7f,w
    0000BD  00AD  movwf 0x2d
    0000BE  082D   movf 0x2d,w
    0000BF  1D03  btfss STATUS,2
    0000C0  28C3   goto _00119_DS_
    0000C1  30FF  movlw 0xff
    0000C2  2902   goto _00115_DS_

[Molnár Károly]

For this reason no need to switch bank. The 0x70-0x7F area can be achieved same place in each bank. See it the Complete Mid-Range Reference Manual document on the 103 side.

[Tom Li]

This old bug should be closed as invalid.

It's well known to all PIC programmers that 0x70 to 0x7F at the end of a memory bank is "common RAM" and these bytes are globally accessible from all banks. For example, SDCC currently uses it as a software stack STK00 to STK15 for passing arguments across different memory banks.

[Benedikt Freisen]

Alright. Let's close it.