Arithmetic and Logic
g Instructions
Hsiao-Lung
H
i L
Chan
Ch
Dept Electrical Engineering
Chang Gung University, Taiwan
chanhl@mail cgu edu tw
[email protected]
Find the sum of the values from 40H to 43H. Put the sum in
fileReg locations 6 (low byte) and 7 (high byte)
L_Byte
H_Byte
N_1
N_2
N_3
N 4
N_4
EQU
EQU
MOVLW
MOVWF
ADDLW
BNC
INCF
ADDLW
BNC
INCF
ADDWF
…
ADDLW
BNC
INCF
MOVWF
0x6
0x7
0x0
H_BYTE
0x40, W
N_1
H_byte, F
0x41
N_2
H_byte,
y ,F
0x42, W
0x43,W
,
N_4
H_byte, F
L Byte
L_Byte
2
Add 16-bit numbers of 3CE7H and 3B8DH. Put the sum in
fileReg locations 6 (low byte) and 7 (high byte)
L_Byte
H_Byte
EQU
EQU
MOVLW
MOVWF
MOVLW
MOVWF
0x6
0x7
0x8D
L BYTE
L_BYTE
0x3B
H_BYTE
MOVLW
ADDWF
MOVLW
ADDWFC
0xE7
L_BYTE,, F
0x3C
H_BYTE, F
3
BCD ((binaryy coded decimal)) number system
y

Unpacked BCD


59 is represented by “0000 0101” and “0000 1001”
Packed BCD


59 is represented
p
byy 59H “0101 1001”
Efficient in storing data
4
DAW instruction
MOVLW
ADDLW
DAW
0x47
; WREG = 47H
0x25
; WREG = 6CH, DC = 0, C = 0
; Adjust for BCD addition by adding 6 (WREG=72H)
MOVLW
ADDLW
DAW
0x09
; WREG = 09H
0x08
; WREG = 11H, DC = 1, C = 0
; Adjust for BCD addition by adding 6 (WREG=17H)
MOVLW
ADDLW
DAW
0x52
; WREG = 52H
0x87
; WREG = D9H,, DC = 0,, C =1
; Adjust for BCD addition by adding 60H (WREG=39H)
MOVLW
ADDLW
DAW
0x57
; WREG = 57H
0x77
; WREG = CEH, DC = 0, C =1
; Adjust for BCD addition by adding 66H (WREG=34H)
Add 0110 to lower 4 bits if lower nibble > 9 or if DC = 1
Add 0110 to upper 4 bits if upper nibble >9 or if C = 1
5
Subtraction of unsigned
g
numbers
MOVLW
SUBLW
0x23
0x3F
; WREG = 3F – WREG
3F – 23 = 3F + 2’s complement of 23
= 3F + DC + 1 = 1 1C
C = 1 N = 0 (D7 is negative flag)
6
Subtract 4C – 6E using
g SUBWF
MYREG
NEXT
EQU
Q
MOVLW
MOVWF
MOVLW
SUBWF
BNN
NEGF
MOVWF
0x20
0x4C
MYREG
0x6E
MYREG, W
NEXT
WREG
MYREG
; WERG = MYREG - WREG
; take 2’s complement
4C – 6E = 4C + 91 + 1 = DE
C = 0 N = 1 (negative,
(
i
FF DE 1 -22)
FF-DE+1,
22)
7
Subtract two 16-bit numbers: 2762H - 1296H. Put the
difference in fileReg locations 6 (low byte) and 7 (high byte)
L_Byte
H_Byte
EQU
EQU
MOVLW
MOVWF
MOVLW
MOVWF
0x6
0x7
0x62
L BYTE
L_BYTE
0x27
H_BYTE
MOVLW
SUBWF
0x96
L_BYTE,, F
MOVLW
SUBWFC
0x12
H BYTE F
H_BYTE,
; F = F – W = 62 – 96 = CCH
; C = borrow = 0, N = 1
; F = F – W – borrow
; = 27 – 12 – 1 = 14H
; 2762H - 1296H = 14CCH
8
Multiplication
p
of unsigned
g
numbers
MOVLW
MULLW
0x25
0x65
25H x 65H = E99H
special function registers
PRODH = 0EH
PRODL = 99H
9
Division of unsigned numbers by repeat subtraction
NUM
MYQ
MYNMB
MYNDEN
EQU
EQU
EQU
EQU
0x19
0x20
D’95’
D’10’
D
10
B1
CLRF
MOVLW
MOVWF
MOVLW
INCF
SUBWF
BC
DECF
ADDWF
MYQ
MYNMB
NUM
MYDEN
MYQ, F
NUM, F
B1
MYQ, F
NUM, F
; reminder
; quotient
; numerator
; denominator
; keep subtraction until C = 0
10
Convert an 8-bit hexadecimal to decimal. Save the digits in
location 0x22
0x22, 0x23
0x23, and 0x24,
0x24
NUME
QU
RMND_L
RMND M
RMND_M
RMND_H
MYNUM
MYNDEN
EQU
EQU
EQU
EQU
EQU
EQU
EQU
MOVLW
MOVWF
MOVLW
CLRF
D_1 INCF
SUBWF
BC
0x15
0x20
0x22
0x23
0x24
0xFD
D’10’
; reminder
; quotient
MYNUM
NUME
MYDEN
QU
QU, F
NUME, F
D_1
ADDWF
DECF
MOVFF
NUME, F
QU, F
NUME, RMND_L
MOVFF
CLRF
D_2 INCF
SUBWF
BC
ADDWF
DECF
MOVFF
QU, NUME
QU, F
QU, F
NUME, F
D_2
NUME, F
QU, F
NUME RMND_M
NUME,
RMND M
MOVFF
QU, RMND_H
11
Signed
g
number arithmetic

Positive vs. negative numbers

Range for 8-bit number


Unsigned numbers: 0 ~ 255
Signed numbers: -128 ~ 127
12
Overflow in signed
g
number operation
p

OV is set if either two conditions occurs
1.
2.
A carry from D6 to D7 but no carry out of D7 (C=0)
A carry from D7 out (C=1) but no carry from D6 to D7
MOVLW
ADDLW
+D’96’
+D’70’
0
MOVLW
ADDLW
-D’128’
-D
D’2’
2
; 1000 0000 + 1111 1110 = 0111 1110 (7EH)
; N = 0, OV = 1, sum = 126
; condition 2
; 0110
0 0 0000 + 0100
0 00 0110
0 0 = 1010
0 0 0110
0 0 (A6H)
( 6 )
; N = 1, OV = 1, sum = -90
; condition 1
13
Overflow in signed
g
number operation
p
(cont.)
(
)
MOVLW
ADDLW
-D’2’
-D’5’
MOVLW
ADDLW
+D’7’
+D’18’
+D
18
; 1111 1110 + 1111 1011 = 1111 1001 (F9H)
; N = 1, OV = 0, sum = -7
; 0000 0111 + 0001 0010 = 0001 1001 (19H)
; N = 0, OV = 0, sum = 25
; condition 2
14
Logic
g operations
p



ANDLW K
IORLW K
XORLW K
; Inclusive OR
; Exclusive OR
15
RB2 and RB5 of PORTB are used to control an
outdoor light and indoor light respectively.
respectively
BCF
BCF
BSF
BCF
TRISB, 2
TRISB, 5
PORTB, 2
PORTB, 5
BCF
BCF
MOVLW
IORWF
MOVLW
ANDWF
TRISB, 2
TRISB, 5
B’00000100’
B
00000100
PORTB, F
B’1101111’
B
1101111
PORTB, F
16
Test PortB to see whether it has value 45H
CLRF
CLRF
SETF
MOVLW
XORWF
BNZ
MOVLW
MOVWF
EXIT
…
TRISC
PORTC
TRISB
0x45
PORTB W
PORTB,
EXIT
0x99
PORTC
17
Compare
p
instructions
18
Monitor PORTD for the value 63H
SETF
MOVLW
BACK CPFSEQ
BRA
TRISD
0x63
PORTD
BACK
19
PORTD is connected to a temperature sensor.
Test it for the value 75
if (T
( > 75))
GREG=T;
else
if (T<75)
LREG=T;
else
WREG=T;
LREG
GREG
LEQ
OVER
EQU
Q
EQU
SETF
MOVLW
CPFSGT
BRA
MOVFF
BRA
CPFSLT
BRA
MOVFF
…
0x20
0x21
TRISD
D’75’
PORTD
LEQ
PORTD, GREG
OVER
PORTD
OVER
PORTD LREG
PORTD,
20
Rotate instructions
7
6
5
4
3
2
1
0
C
Figure 2.17 Operation performed by the rlcf f,d,a instruction
C
7
6
5
4
3
2
1
0
Figure 2.19 Operation performed by the rrcf f,d,a instruction
7
6
5
4
3
2
1
0
Figure 2.18 Operation performed by the rlncf f,d,a instruction
7 6
5 4 3
2 1 0
Figure 2.20 Operation performed by the rrncf f,d,a instruction
21
Do multiplication/division of unsigned numbers by
rotating left/right through carry
MYREG EQU
Q
0x20
MOVLW 0x25
MOVWF MYREG
MYREG EQU
Q
0x20
MOVLW 0xD5
MOVWF MYREG
BCF
RLCF
STATUS, C
MYREG F
MYREG,
BCF
RRCF
STATUS, C
MYREG F
MYREG,
BCF
RLCF
STATUS, C
MYREG, F
BCF
RRCF
STATUS, C
MYREG, F
22
Do multiplication/division of signed numbers by
rotating left/right through carry
MYREG EQU
Q
0x20
MOVLW 0xD5
MOVWF MYREG
BCF
RLCF
STATUS, C
MYREG F
MYREG,
BCF
RLCF
STATUS, C
MYREG, F
MYREG EQU
Q
0x20
MOVLW 0xD5
MOVWF MYREG
BCF
BTFSC
BSF
RRCF
STATUS, C
MYREG 7
MYREG,
STATUS, C
MYREG, F
BCF
BTFSC
BSF
RRCF
STATUS, C
MYREG 7
MYREG,
STATUS, C
MYREG F
MYREG,
23
Series a byte of data
Transfer value 41H seriallyy via pin
p RB1. Put one high
g at the
start and end of the data. Send the LSB first.
RCNT EQU
Q
MYREG EQU
BCF
MOVLW
MOVWF
MOVLW
MOVWF
0x20
0x21
TRISB, 1
0x41
MYREG
0x8
RCNT
BSF
AGAIN RRCF
BNC
BSF
BRA
OVER BCF
NEXT DECF
BNZ
BSF
PORTB,, 1
MYREG, F
OVER
PORTB, 1
NEXT
PORTB 1
PORTB,
RCNT, F
AGAIN
PORTB, 1
24
Input series data:
Bring
g in a byte
y of data seriallyy via RC7 and save it in file
register location 0x21. The byte comes in with the LSB first.
RCNT EQU
Q
MYREG EQU
0x20
0x21
BSF
MOVLW
MOVWF
AGAIN BTFSC
BSF
BTFSS
BCF
RRCF
DECF
BNZ
TRISC, 7
0x8
RCNT
PORTC, 7
STATUS, C
PORTC, 7
STATUS, C
MYREG F
MYREG,
RCNT, F
AGAIN
25
Find number of 1s in a g
given byte
y
R1
EQU
Q
COUNT EQU
VALREG EQU
CLRF
MOVLW
MOVWF
MOVLW
MOVWF
AGAIN RLCF
BNC
INCF
NEXT DECF
BNZ
0x20
0x21
0x22
R1
0x8
RCNT
0x97
VALREG
VALREG, F
NEXT
R1, F
COUNT F
COUNT,
AGAIN
26
SWAPF fileReg,
g d
MYREG EQU
MOVLW
MOVWF
SWAPF
0x20
0x72
MYREG
MYREG, F
27
Packed BCD to ASCII conversion
BCD_VAL EQU
Q
L_ASC
EQU
H_ASC
EQU
0x29
0x06
0x07
MOVLW BCD_VAL
ANDLW 0x0F
IORLW 0x30
MOVWF L_ASC
MOVLW BCD_VAL
ANDLW 0xF0
SWAP
WREG W
WREG,
IORLW 0x30
MOVWF H_ASC
H ASC
28
ASCII to p
packed BCD conversion
MYBCD EQU
Q
MOVLW
ANDLW
MOVWF
SWAP
MOVLW
ANDLW
IORWF
0x20
A’4’
0x0F
MYBCD
MYBCD, F
A
A’7’
7
0x0F
MYBCD, F
29
Reference


M.A. Mazidi, R.D. Mckinlay, D Causey, PIC Microcontroller
and Embedded Systems Using Assembly and C for PIC18,
Pearson Education Inc., 2008.
Han-Way Huang, PIC Microcontroller: An Introduction to
Software and Hardware Interfacing, Thomson Delmar
L
Learning,
i
2005.
2005
30