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Microcontroller Kits Simple
Mikrokontroller 89s51 Trainer
Super
Mikrokontroller Trainer 89s51
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Subroutine Multiplication for 8051 Microcontroller
;================================================================== MUL8: anl PSW, #0E7H ; Register Bank 0
acall Cr0 ; 2's comp -> Mag/Sign
acall Cr1 ; 2's comp -> Mag/Sign
acall UMUL8
acall Mr0r1 ; Mag/Sign -> 2's Comp
ret
;================================================================== ; subroutine UMUL8 ; 8-Bit x 8-Bit to 16-Bit Product Unsigned Multiply ; ; input: r0 = multiplicand X ; r1 = multiplier Y ; ; output: r1, r0 = product P = X x Y. ; ; alters: acc ;================================================================== UMUL8: push b
mov a, r0 ; read X and ...
mov b, r1 ; ... Y
mul ab ; multiply X and Y
mov r1, b ; save result high ...
mov r0, a ; ... and low
pop b
ret
;====================================================================
; subroutine MUL816
; 8-Bit x 16-Bit to 32-Bit Product signed Multiply
; 2's Complement format
;
; input: r0 = multiplicand X
; r3, r2 = multiplier Y
;
; output: r3, r2, r1, r0 = product P = X x Y (r3 = sign extension)
;
; calls: Cr0, Cr2r3, Mr0r3
;
; alters: acc, C, Bits 21H & 22H
;====================================================================
MUL816: push b
anl PSW, #0E7H ; Register Bank 0
acall Cr0 ; 2's comp -> Mag/Sign
acall Cr2r3 ; 2's comp -> Mag/Sign
mov a, r0 ; load X low byte into acc
mov b, r2 ; load Y low byte into B
mul ab ; multiply
push acc ; stack result low byte
push b ; stack result high byte
mov a, r0 ; load X into acc again
mov b, r3 ; load Y high byte into B
mul ab ; multiply
pop 00H ; recall X*YL high byte
add a, r0 ; add X*YL high and X*YH low
mov r1, a ; save result
clr a ; clear accumulator
addc a, b ; a = b + carry flag
mov r2, a ; save result
pop 00H ; get low result
mov r3, #0
acall Mr0r3 ; Mag/Sign -> 2's Comp
pop b
ret
;==================================================================== ; subroutine MUL16 ; 16-Bit x 16-Bit to 32-Bit Product Signed Multiply ; 2's Complement format ; ; input: r1, r0 = multiplicand X ; r3, r2 = multiplier Y ; ; output: r3, r2, r1, r0 = product P = X x Y ; ; calls: UMUL16, Cr0r1, Cr2r3, Mr0r3 ; ; alters: acc, C, Bits 21H & 22H ;==================================================================== MUL16: anl PSW, #0E7H ; Register Bank 0
acall Cr0r1 ; 2's comp -> Mag/Sign
acall Cr2r3 ; 2's comp -> Mag/Sign
acall UMUL16
acall Mr0r3 ; Mag/Sign -> 2's Comp
ret
;==================================================================== ; subroutine UMUL16 ; 16-Bit x 16-Bit to 32-Bit Product Unsigned Multiply ; ; input: r1, r0 = multiplicand X ; r3, r2 = multiplier Y ; ; output: r3, r2, r1, r0 = product P = X x Y ; ; alters: acc, C ;==================================================================== UMUL16: push B
push dpl
mov a, r0
mov b, r2
mul ab ; multiply XL x YL
push acc ; stack result low byte
push b ; stack result high byte
mov a, r0
mov b, r3
mul ab ; multiply XL x YH
pop 00H
add a, r0
mov r0, a
clr a
addc a, b
mov dpl, a
mov a, r2
mov b, r1
mul ab ; multiply XH x YL
add a, r0
mov r0, a
mov a, dpl
addc a, b
mov dpl, a
clr a
addc a, #0
push acc ; save intermediate carry
mov a, r3
mov b, r1
mul ab ; multiply XH x YH
add a, dpl
mov r2, a
pop acc ; retrieve carry
addc a, b
mov r3, a
mov r1, 00H
pop 00H ; retrieve result low byte
pop dpl
pop B
ret
;================================================================= Cr0: mov a, r0 ; read X into accumulator
jb acc.7, Cr0a ; X is negative if bit 7 is 1
clr 21H ; clear sign bit if 'positive'
ret ; done
Cr0a: cpl a ; X negative, find abs value
inc a ; XA = complement(XT)+1
mov r0, a ; save magnitude
setb 21H ; set sign bit if 'negative'
ret
;================================================================= ; subroutine Cr1 ; 8-Bit 2's Complement -> magnitude / Sign Bit Conversion ; ; input: r1 = signed byte ; ; output: r1 = magnitude ; Bit 22H = sign (22H is set if r1 is a negative number) ; ; alters: acc ;================================================================= Cr1: mov a, r1 ; read X into accumulator
jb acc.7, Cr1a ; X is negative if bit 7 is 1
clr 22H ; clear sign bit if 'positive'
ret ; done
Cr1a: cpl a ; X negative, find abs value
inc a ; XA = complement(XT)+1
mov r1, a ; save magnitude
setb 22H ; set sign bit if 'negative'
ret
;===================================================================
; subroutine Cr0r1
; 16-Bit 2's Complement -> magnitude / Sign Bit Conversion
;
; input: r1, r0 = signed word
;
; output: r1, r0 = magnitude
; Bit 21H = sign (21H is set if negative number)
;
; alters: acc, C
;===================================================================
Cr0r1: mov a, r1 ; high byte into accumulator
jb acc.7, c0a ; negative if bit 7 is 1
clr 21H ; clear sign bit if 'positive'
ret ; done
c0a: setb 21H ; set sign flag
mov a, r0 ; number is negative
cpl a ; complement
add a, #1 ; and add +1
mov r0, a
mov a, r1 ; get next byte
cpl a ; complement
addc a, #0
mov r1, a
ret
;====================================================================
; subroutine Cr2r3
; 16-Bit 2's Complement -> magnitude / Sign Bit Conversion
;
; input: r3, r2 = signed word
;
; output: r3, r2 = magnitude
; Bit 22H = sign (22H is set if negative number)
;
; alters: acc, C
;====================================================================
Cr2r3: mov a, r3 ; read high into accumulator
jb acc.7, c1a ; negative if bit 7 is 1
clr 22H ; clear sign bit if 'positive'
ret ; done
c1a: setb 22H ; set sign flag
mov a, r2 ; number is negative
cpl a ; complement
add a, #1 ; and add +1
mov r2, a
mov a, r3 ; get next byte
cpl a ; complement
addc a, #0
mov r3, a
ret
;====================================================================
; subroutine Cr4r5
; 16-Bit 2's Complement -> magnitude / Sign Bit Conversion
;
; input: r5, r4 = signed word
;
; output: r5, r4 = magnitude
; Bit 22H = sign (22H is set if negative number)
;
; alters: acc, C
;====================================================================
Cr4r5: mov a, r5 ; read high into accumulator
jb acc.7, c3a ; negative if bit 7 is 1
clr 22H ; clear sign bit if 'positive'
ret ; done
c3a: setb 22H ; set sign flag
mov a, r4 ; number is negative
cpl a ; complement
add a, #1 ; and add +1
mov r4, a
mov a, r5 ; get next byte
cpl a ; complement
addc a, #0
mov r5, a
ret
;====================================================================
; subroutine Cr0r3
; 32-Bit 2's Complement -> magnitude / Sign Bit Conversion
;
; input: r3, r2, r1, r0 = signed word
;
; output: r3, r2, r1, r0 = magnitude
; Bit 21H = sign (21H is set if negative number)
;
; alters: acc
;====================================================================
Cr0r3: mov a, r3 ; read high into accumulator
jb acc.7, c2a ; negative if bit 7 is 1
clr 21H ; clear sign flag if 'positive'
ret ; done
c2a: setb 21H ; set sign flag
mov a, r0 ; number is negative
cpl a ; complement
add a, #1 ; and add +1
mov r0, a
mov a, r1 ; get next byte
cpl a ; complement
addc a, #0
mov r1,a
mov a, r2 ; get next byte
cpl a ; complement
addc a, #0
mov r2,a
mov a, r3 ; get next byte
cpl a ; complement
addc a, #0
mov r3, a
ret ; done
;==================================================================
; subroutine Mr0
; 8-Bit magnitude / Sign Bit -> 2's Complement Conversion
;
; input: r0 = magnitude
; Bits 21H & 22H = sign bits of operands X and Y
; (set if negative)
;
; output: r0 = signed byte
;
; alters: acc
;==================================================================
Mr0: jb 21H, Mr0b ; test X sign
jb 22H, Mr0a ; test Y sign
ret
Mr0b: jnb 22H, Mr0a
ret
Mr0a: mov a, r0 ; if r0 negative, get abs value
cpl a ; complement magnitude of X
inc a ; r0 = complement(r0)+1
mov r0, a ; save in 2's complement
ret ; done
;====================================================================
; subroutine Mr0r1
; 16-Bit magnitude / Sign Bit -> 2's Complement Conversion
;
; input: r1, r0 = magnitude
; Bits 21H & 22H = sign bits of operands X and Y
; (set if negative)
;
; output: r1, r0 = signed word
;
; alters: acc, C
;====================================================================
Mr0r1: jb 21H, Mr0r1b ; test X sign
jb 22H, Mr0r1a ; test Y sign
ret
Mr0r1b: jnb 22H, Mr0r1a
ret
Mr0r1a: mov a, r0 ; negate number
cpl a ; complement
add a, #1 ; and add +1
mov r0, a
mov a, r1 ; get next byte
cpl a ; complement
addc a, #0
mov r1, a
ret
;====================================================================
; subroutine Mr0r3
; 32-Bit magnitude / Sign Bit -> 2's Complement Conversion
;
; input: r3, r2, r1, r0 = magnitude
; Bits 21H & 22H = sign bits of operands X and Y
; (set if negative)
;
; output: r3, r2, r1, r0 = signed word
;
; alters: acc, C
;====================================================================
Mr0r3: jb 21H, Mr0r3b ; test X sign
jb 22H, Mr0r3a ; test Y sign
ret
Mr0r3b: jnb 22H, Mr0r3a
ret
Mr0r3a: mov a, r0 ; negate number
cpl a ; complement
add a, #1 ; and add +1
mov r0, a
mov a, r1 ; get next byte
cpl a ; complement
addc a, #0
mov r1, a
mov a, r2 ; get next byte
cpl a ; complement
addc a, #0
mov r2, a
mov a, r3 ; get next byte
cpl a ; complement
addc a, #0
mov r3, a
ret ; done
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