INSTRUCTION DESCRIPTIONS
MOTOROLA
INSTRUCTION SET DETAILS
A - 85
Note that the divide routine used in the previous example assumes that the sign-
extended 56-bit signed fractional dividend is stored in the A accumulator and that the 24-
bit signed fractional divisor is stored in the X0 register. This routine produces a
full 24-bit
signed quotient and a 48-bit signed remainder.
This routine may be greatly simplified for the case in which only positive, fractional oper-
ands are used to produce a 24-bit positive quotient and a 48-bit positive remainder, as
shown in the following example:
1-Quadrant division, 24-bit unsigned quotient, 48-bit unsigned remainder
AND #$FE,CCR
;clear carry bit C (quotient sign bit)
REP #$18
;form a 24-bit quotient and remainder
DIV X0,A
;form quotient in A0, remainder in A1
ADD X0,A
;restore remainder in A1
Note that this routine assumes that the 56-bit positive, fractional, sign-extended dividend
is stored in the A accumulator and that the 24-bit positive, fractional divisor is stored in
the X0 register. After execution, the 24-bit positive fractional quotient is stored in the A0
register; the LS 24 bits of the 48-bit positive fractional remainder are stored in the A1 reg-
ister.
There are many variations possible when choosing a suitable division routine for a given
application. The selection of a suitable division routine normally involves specification of
the following items:
1. the number of bits of precision in the dividend;
2. the number of bits of precision N in the quotient;
3. whether the value of N is fixed or is variable;
4. whether the operands are unsigned or signed;
5. whether or not the remainder is to be calculated.
DIV
Divide Interation
DIV
Содержание DSP56K
Страница 12: ...xii LIST of TABLES MOTOROLA List of Tables Continued Table Page Number Title Number ...
Страница 13: ...MOTOROLA DSP56K FAMILY INTRODUCTION 1 1 SECTION 1 DSP56K FAMILY INTRODUCTION ...
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Страница 50: ...DATA ALU SUMMARY 3 20 DATA ARITHMETIC LOGIC UNIT MOTOROLA ...
Страница 51: ...MOTOROLA ADDRESS GENERATION UNIT 4 1 SECTION 4 ADDRESS GENERATION UNIT ...
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Страница 125: ...MOTOROLA PROCESSING STATES 7 1 SECTION 7 PROCESSING STATES STOP WAIT EXCEPTION NORMAL RESET ...
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