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useless R7

huang faqian 

bit CheckPacket(void)
{
        unsigned char idata *pBuf = g_UART0Buf;
        unsigned char len, checksum;

        if (*pBuf == PACKET_START_ID / 256)
        {
                pBuf++;
                if (*pBuf == PACKET_START_ID % 256)
                {
                        pBuf++;
                        len = *pBuf;
                        checksum = *pBuf;
                        pBuf++;
                        len++;
                        do
                        {
                                checksum += *pBuf;
                                pBuf++;
                                len--;
                        } while (len);
                        if(!checksum)
                        {
                                return 1;
                        }
                }
        }
        return 0;
}

             ; FUNCTION CheckPacket (BEGIN)
                                           ; SOURCE LINE # 13
                                           ; SOURCE LINE # 14
                                           ; SOURCE LINE # 15
                 E     MOV     R7,#LOW g_UART0Buf
;---- Variable 'pBuf' assigned to Register 'R7' ----
                                           ; SOURCE LINE # 18
                       MOV     R0,AR7
                       MOV     A,@R0
                       XRL     A,#07H
                 R     xJNZ    ?C0001
                                           ; SOURCE LINE # 19
                                           ; SOURCE LINE # 20
                       INC     R7
                                           ; SOURCE LINE # 21
                       INC     R0
                       MOV     A,@R0
                       XRL     A,#0EH
                 R     xJNZ    ?C0001
                                           ; SOURCE LINE # 22
                                           ; SOURCE LINE # 23
                       INC     R7
                                           ; SOURCE LINE # 24
                       INC     R0
                       MOV     A,@R0
                       MOV     R6,A
;---- Variable 'len' assigned to Register 'R5' ----
                       MOV     R5,A
                                           ; SOURCE LINE # 25
;---- Variable 'checksum' assigned to Register 'R6' ----
                                           ; SOURCE LINE # 26
                       INC     R7
                                           ; SOURCE LINE # 27
                       INC     R5
             ?C0005:
                                           ; SOURCE LINE # 29
                                           ; SOURCE LINE # 30
                       MOV     R0,AR7
                       MOV     A,@R0
                       ADD     A,R6
                       MOV     R6,A
                                           ; SOURCE LINE # 31
                       INC     R7
                                           ; SOURCE LINE # 32
                 R     DJNZ    R5,?C0005
                                           ; SOURCE LINE # 33
                                           ; SOURCE LINE # 34
                 R     xJNZ    ?C0001
                                           ; SOURCE LINE # 35
                                           ; SOURCE LINE # 36
                       SETB    C
                       RET
                                           ; SOURCE LINE # 37
                                           ; SOURCE LINE # 38
                                           ; SOURCE LINE # 39
             ?C0001:
                                           ; SOURCE LINE # 40
                       CLR     C
                                           ; SOURCE LINE # 41
             ?C0007:
                       RET
             ; FUNCTION CheckPacket (END)

Parents
  • 0 in reply to Mike Kleshov

    He must have mistyped. Probably meant to say "use less R7".

    Try searching the documentation for:

    #pragma USE_LESS(Rn)

    It might allow you to specify usage of individual registers.

    There might also be:

    #pragma USE_MORE(Rn)

    And finally:

    #pragma USE_WITH_EQUAL_AMOUNTS_TO_AVOID_SUGGESTION_OF_FAVOURITISM(Rn)

Reply
  • 0 in reply to Mike Kleshov

    He must have mistyped. Probably meant to say "use less R7".

    Try searching the documentation for:

    #pragma USE_LESS(Rn)

    It might allow you to specify usage of individual registers.

    There might also be:

    #pragma USE_MORE(Rn)

    And finally:

    #pragma USE_WITH_EQUAL_AMOUNTS_TO_AVOID_SUGGESTION_OF_FAVOURITISM(Rn)

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