;-----------------------------------------------------------------
; EX64.ASM  COUNT ONES		C.P. Diduch 2001
;
; Count the number of ones in the memory variable DATA 
; and store the number in memory variable SUM.
;
;    Author(s):
; Signature(s):                              Date:
;-----------------------------------------------------------------
        .ORG    0x0000          ; "variable assignments in RAM"
DATA:   .DS     1               ; unsigned DATA, SUM ;
SUM:    .DS     1               ;
				;
        .ORG    0x8000          ; "assign the following to ROM"
				;
                                ; void main(void) {
                                ;
                                ; do {
L0:     XOR     R0, R0, R0      ;    SUM = 0 ;
	STOREM	SUM, R0		;
        LOADP   R0, 0x0001      ;    DATA = inport(0x0001) ;
        STOREM  DATA, R0;       ;
        XOR     R7, R7, R7      ;    i = 0;   // Reg. var. in R7.
L1:     SUBL    NULL, R7, 16    ;    while (i < 16) { 
        JMPNC   L3              ;
                                ;
        SHIFTU  R0, R0, 1(NULL) ;       if (Bit-i of DATA == 1) {    
        JMPNC   L2              ;
        LOADM   R1, SUM         ;          SUM = SUM + 1 ;
        ADDL    R1, R1, 1       ;
        STOREM  SUM, R1         ;          }
L2:     ADDL    R7, R7, 1       ;       i = i + 1 ;
        JMP     L1              ;       }
                                ;
L3:     LOADM   R3, SUM         ;
        STOREP  0x0002, R3      ;    outport(0x0002, SUM) ;
        JMP     L0              ;    }