0010 D,R4 BASE ADDRESS OF THE EIGHT DISPLAYED MEMORY 00001100 2 0C F3 12 243 LOCATIONS, REGISTER 4: TEMPORARILY PCH AFTER BREAK. R5 REGISTER 5: TEMPORARI LY PCL AFTER BREAK R6 REGISTER 6: TEMPORARI LY 01 AFTER BREAK R7 REGISTER 7: TEMPORARI LY S AFTER BREAK. LAST 4 DISPLAYED MEMORY LOCATIONS. P SINGLE LEVEL OF STORAGE FOR PREVIOUS DATA AT BREAKPOINTS. COL COLUMN OF KEY CURRENTLY BEING PROCESSED TX.TY TEMPORARY STORAGE FOR X (IN DISPLAY) OR Y 16 16 10 10 0011 0012 0013 0014-0017 0018 11111111 2 WHICH DOESN'T HAPPEN .... FF 16 ADD AN EXTRA 1 255 10 000011002 UNTIL WE 0C 16 12io 243io 11110011 2 + F3 16 16 0019 001A 1l6 + 1 000000002 1a lio 256 10 (VARIOUS PLACES).
USERNMI ADDRESS OF USER'S NMI PROGRAM USERIRQ ADDRESS OF USER'S IRQ PROGRAM RECAL CONTAINS PC RECALCULATION FACTOR FOR BREAK QUAD DISPLAY X-3,X-2,X-1 ,X ON THE DISPLAY; THEN I DISPLAY STROBE KEYBOARD, MULTIPLEX DISPLAY, RETURN AND THEN TREAT THE OUTPUT CARRY AS INDICATING THE ABSENCE OF A BORROW FROM THE HIGHER ORDERS. THE NUMBER (ONE'S-COMPLEMENT + 1) IS CALLED THE TWO'S-COMPLEMENT OF A NUMBER: 001C001D 001E,001F 001B FE00 FE0C BINARY HEXADECIMAL DECIMAL 00000001 2 01 i6 +1 1 O IIIIIIH2 111111102 FF FE +0i 0 or - 0 !
0 -ho -2io FE5E FE60 FE64 FE66 FE6F FE7A FE88 FEA0 WITH KEY INFORMATION MHEXTD DISPLAY A MEMORY BYTE ON RIGHT OF DISPLAY 16 16 RDHEXTD DISPLAY A ON RIGHT OF DISPLAY QHEXTD1 DISPLAY X & X+1 ON DISPLAYS 1,2,3 & 4 QHEXTD2 DISPLAY X & X+1 ON DISPLAYS Y - 2 , Y - 1 , Y & Y+1 DHEXTD DISPLAY A ON DISPLAYS Y & Y+1 HEXTD DISPLAY BOTTOM 4 BITS OF A ON DISPLAY Y QDATFET FETCH AN ADDRESS INTO LOCATIONS X & X+1 COM16 INCREMENT & COMPARE TWO 16 BIT NOS X+6,X+7 & X+8,X+9 NOINC COMPARE X+6,X+7 & X+8,X+9 FOR EQUALITY PUTBYTE A TO TAPE, DO 1 START & 1 STOP BITS, NO PARITY WAIT WAIT FOR CASSETTE TIMING % WAIT HALT^THE WAIT GETBYTE TAPE TO A, WAIT FOR START BIT, CENTRE TIMING F4 16 - 1 2 i 0 80 16 -128 1 O 0IIIIIH2 7F 16 +127 l 0 SO A BYTE CAN BE TREATED AS A 'SIGNED BINARY NUMBER' IN THE RANGE +127 0 -128, OR AS A BINARY NUMBER IN THE RANGE 0 +255.
NOW THE SUBTRACTION ABOVE SHOULD BE CLEAR : INTERNALLY, THE MICRO- 111101002 100000002 PROCESSOR ONE'S-COMPLEMENTS ONE OF THE NUMBERS AND THEN EXECUTES A NORMAL ADDITON WITH CARRY. FEA6 FEB1 FECD FED0 FEDD FEF3 FF04 FFB3 1.4 BINARY CODED DECIMAL (BCD) ARITHMETIC 99 16 LOOKS VERY LIKE99 1 0 THEY BEHAVE THE SAME WAY AS THEY ARE MOVED AROUND AND UNDERGO LOGICAL OPERATIONS SINCE THEY ARE WRITTEN THE SAME WAY.
THE BINARY REPRESENTATION OF 99 1 0 WOULD RESET ENTRY TO MONITOR RESTART RE-ENTRY TO RUNNING MONITOR BREAK ENTRY TO MONITOR FROM BRK INSTRUCTION, DISPLAY CPU FONT SEVEN SEGMENT PICTURES OF THE HEX DIGITS RECAL CONTAINS PC RECALCULATION FACTOR FOR BREAK NORMALLY BE 011000112, AND OF 99 i 6 IT WOULD BE 10011001^ WE NOW DEFINE THE BINARY CODED DECIMAL VERSION OF 99 1 0 AS BEING THE BINARY REPRESENTATION OF THE DECIMAL DIGITS IN THE ORIGINAL POSITIONAL NOTATION, MAKING THE DIFFERENCE BETWEEN THE BINARY REPRESENTATIONS OF 99 16 & 99 1 0 A MATTER OF SUPSCRIPTS: FFEA 99 16 =10011001 2 99 10 = 10011001 B.C.D. THE B.C.D. AND BINARY NUMBERS DIFFER IN HANDLING ONLY IN ARITHMETIC:
?9i6 79io 22 16 + BUT 22 10 + 9B 16 101 10 THE MICROPROCESSOR CAN BE TOLD' WHICH TYPE OF ARITHMETIC TO CARRY OUT, BY SETTING (PUTTING A ONE INTO) OR CLEARING (PUTTING A ZERO INTO) AN INTERNAL BIT, THE 'DECIMAL MODE' FLAG.