;
; SYSLIB Module Name:  SEVAL4
; Author:  Richard Conn
; SYSLIB Version Number:  2.0
; Module Version Number:  1.0
; Module Entry Points:
;       EVAL2
; Module External References:
;       None
;

;
;  EVAL2 --
;       Convert the string of ASCII binary digits pointed to by HL
; into a binary value; string is converted until invalid digit is
; encountered.
;       On return, HL points to error character, DE=value, A=E (low
; order 8 bits of value).  BC not affected.
;

EVAL2::
       PUSH    B       ; SAVE BC
       LXI     D,0     ; SET DE=0 INITIALLY

;  Get next digit and check for '0' - '9'
E2L:
       MOV     A,M     ; GET BYTE
       SUI     '0'     ; CHECK FOR RANGE
       JC      DONE
       CPI     2
       JNC     DONE

;  Multiply DE by 2
MUL2:
       PUSH    H       ; SAVE HL
       LXI     H,0     ; ACC=0
       DAD     D       ; HL=DE
       DAD     D       ; HL=DE+DE
       MOV     D,H     ; DE=HL
       MOV     E,L
       POP     H       ; RESTORE HL
       ADD     E       ; A=A+E
       MOV     E,A
       MOV     A,D     ; ADD TO D IF NECESSARY
       ACI     0

;  Continue
       INX     H       ; PT TO NEXT CHARACTER
       JMP     E2L

;  Done -- Result already in DE; Set A=E
DONE:
       MOV     A,E     ; A=E
       POP     B       ; RESTORE BC

       RET

       END

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