Computer Hardware

Spectra 70

RCA Spectra 70 Training Manual

63 pages

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If

an

attempt

were

made

to

add

the

amount

to

the

balance

with

the

following

instruction:

ASSEMBLY

OPERATION

OPERAND

INSTRUCTION

~---------4------------~

AP

BAL

(3), AMT (5)

~!~~~~~~gN

1

FA1612

141110

13000101110

13020101

General

Register

one

contains

0000

the

result

in

the

balance

BALwould

be

as

follows

and

the

Condition

Code

would

be

set

as

indicated.

EXAMPLE

1

RESULT

BAL

1

30

I

~~

~~

~

{

CC = 2

(pOSITIVE

RESULT)

EXAMPLE

2

RESULT

BAL

I

30

I

~~

~~

~!

~

CC = 3 (OVERFLOW)

Note

that

in

Example

2,

the

Condition

Code

of

3

(overflow)

is

not

an

indication

that

truncation

has

occurred

as

truncation

also

has

occurred

in

Example

1.

The

overflow

setting

is

based

on

the

1

carry

from

the

MSD

of

the

Result

field.

There

is

no

hardware

check

or

error

indication

for

invalid

or

incorrectly

addressed

fields.

It

is

the

re-

sponsibility

of

the

programmer

to

be

sure

that

he

has

addressed

valid

packed

fields.

A

field

may

be

added

to

(or

subtracted

from)

itself

if

desired.

As

an

example,

assume

that

a

field

has

been

used

for

accumulation

and

it

is

desired

to

zero

fill

it

with

a

valid

sign

in

the

rightmost

byte

position.

The

field

WBAL

is

as

follows:

61

WBAL

43

44

45

46

)

02

15

24

3+ )

The

following

instruction

would

zero

fill

and

pre-

serve

the

sign

pOSition:

ASSEMBLY

OPERATION

OPERAND

INSTRUCTION

SP

WBAL(4).

WBAL(4)

GENERATED

INSTRUCTION

General

Register

two

contains

4096

10

30

RESULT

FIELD

WBAL

43 44

45

46

61

t-----------{

00 00

00

0+

MULTIPLY

DECIMAL

Multiplication

may

be

performed

on

two

packed

oper-

ands.

The

result

(product)

replaces

the

first

oper-

and

(multiplicand)

following

execution

of

the

instruc-

tion.

The

number

of

leading

zeros

in

the

multiplicand

should

equal

the

number

of

significant

digits

in

the

multiplier.

If

the

multiplicand

field

has

an

insuf-

ficient

number

of

leading

zeros,

the

high-order

product

digits

are

truncated.

The

programmer

must

ensure

that

fields

are

valid

numerics

as

the

hardware

performs

no

check

of

this

type.

The

Condition

Code

is

not

affected

by

the

exe-

cution

of

this

instruction.

Example

#J

In

this

example

assume

the

two

fields

are

present

in

memory

and

have

been

assigned

the

following

values:

PRCE

07 08

21

21

57

09

22

2+

NUNT

30 31

02\7+

The

item

PRCE,

to

be

multiplied

by

NUNT,

is

not

of

sufficient

length

to

receive

the

product.

It

could

be

moved

to

a

zero-filled

work

area

and

multiplica-

tion

performed

as

follows:

HSM

BEFORE

EXECUTION

HSM

BEFORE

AND

AFTER

EXECUTION

ASSEMBLY

INSTRUCTION

WPRC

OPERATION

OPERAND

MP

WPRC(5)

,NUNT

(2)

~:s~~~~~~gN

I

FC

16

1410

1110 I

Z

10

I

zo0

10

1

210

IZ30

lO

I

GENERAL

REGISTf;R

1 CONTAINS Z00010

HSM

AFTER

EXECUTION

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Reference Manual260 pages

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RCA Spectra 70 Specifications

General

Brand	RCA
Model	Spectra 70
Category	Computer Hardware
Language	English

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