11

Programming Example for Division

MEMORY

LOCATION

OP

CODE

LINE

NO.

ASSEMBLY LANGUAGE

0000

;

0001

. . Program example for a 16-bit by 8-bit divide using 1 CDP1855 MDU

0000

;

0002

. . Gives a 16-bit answer with 8-bit remainder

0000

;

0003

0000

68C22000;

0004

RLDI R2, 2000H

. . Answer is stored at 2000 hex

0004

;

0005

. . Register 2 points to it

0004

68C33000;

0006

RLDI R3, 3000H

. . Dividend is stored at 3000 hex

0008

;

0007

. . Register 3 points to it

0008

68C44000;

0008

RLDI R4, 4000H

. . Divisor is stored at 4000 hex

000C

;

0009

. . Register 4 points to it

000C

;

0010

000C

E067F0;

0011

SEX R4; OUT 7; DC OF0H

. . Write to the control register to use

000F

;

0012

. . clock/2; 1MDU; reset sequence

000F

;

0013

. . counter; and no operation

000F

;

0014

000F

E464;

0015

SEX R4; OUT 4

. . Load the divisor into the X register

0011

;

0016

0011

E06600;

0017

SEX R0; OUT 6; DC 0

. . Load 0 into the Y register

0014

E365;

0018

SEX R3; OUT 5

. . Load the most significant 8 bits of

0016

;

0019

. . the dividend into the Z register

0016

;

0020

0016

E067F2;

0021

SEX R0; OUT 7; DC 0F2H

. . Do the first divide, also resets the

0019

;

0022

. . sequence counter

0019

;

0023

0019

E26D60;

0024

SEX R2; INP 5; IRX

. . Read and store the most significant

001C

;

0025

. . 8 bits of the answer at 2000 hex

001C

;

0026

001C

E067F0;

0027

SEX R0; OUT 7; DC 0F0H

. . Reset the sequence counter

001F

;

0028

001F

E365;

0029

SEX R3; OUT 5

. . Load the 8 least significant 8 bits

0021

;

0030

. . of the original dividend into the Z

0021

;

0031

. . register

0021

;

0032

0021

E067F2;

0033

SEX R0; OUT 7; DC 0F2H

. . Do the second division

0024

;

0034

0024

E26D60;

0035

SEX R2; INP 5; IRX

. . Read and store the least significant

0027

;

0036

. . 8 bits of the answer at 2001 hex

0027

6E;

0037

INP 6

. . Read and store the remainder at 2002

0028

;

0038

. . hex

0000

CDP1855, CDP1855C