; subroutine MULDIV ; 16-Bit x 16-Bit to 32-Bit Product Signed Multiply followed by ; 32-Bit / 16-Bit to 32-Bit Quotient & remainder signed Divide ; 2's Complement Format ; ; input: r1, r0 = multiplicand X ; r3, r2 = multiplier Y ; r5, r4 = divisor Z ; ; output: r3, r2, r1, r0 = quotient Q of division Q = (X x Y) / Z ; r7, r6, r5, r4 = remainder ; Carry C is set if Z = 0, i.e. divide by 0 attempted ; ; calls: UMUL16, UDIV32, Cr0r1, Cr2r3, Cr4r5, Mr0r3 ; ; alters: acc, flags, Bits 21H & 22H
MULDIV: anl PSW, #0E7H ;Register Bank 0 mov a, r4 ;get divisor high byte orl a, r5 ;OR with low byte jnz muld_OK ;divisor OK if not 0 setb C ;else, overflow ret muld_OK: lcall Cr0r1 ;2's comp -> Mag/Sign lcall Cr2r3 ;2's comp -> Mag/Sign lcall UMUL16 jb 21H, divn1 ;test X sign divn: lcall Cr4r5 ;2's comp -> Mag/Sign lcall UDIV32 lcall Mr0r3 ;Mag/Sign -> 2's Comp clr C ;divisor is not 0v
ret divn1: jbc 22H, divn ;test Y sign setb 22H sjmp divn
Source: Maths Subroutines for the 8051 microcontroller, W.G.Marshall 2002
Related topics:
8051 Program - signed 16bit multiply Accumulate table | 8051 Program - signed 16bit multiply Accumulate | 8051 Program - unsigned 8bit multiplication | 8051 Program - signed 32bit division | 8051 Program - unsigned 32bit division | 8051 Program - memory subroutines | 8051 Program - math subroutines | 8051 Program - conversion subroutines
List of topics: 8051
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