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RCA Spectra 70 Training Manual
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DECIMAL
ARITHMETIC
INSTRUCTIONS
Decimal
Add
and
Subtract
The
RCA
70/25
has
four
decimal
arithmetic
instruc-
tions,
Add
Decimal
(AP)
Subtract
Decimal
(SP)
,
Multiply
Decimal
(MP)
,
and
Divide
Decimal
(DP)
•
All
require
operands
to
be
in
packed
format.
The
rightmost
byte
in
each
field
is
assumed
to
contain
the
Sign
in
the
low-order
four
bits.
A
sign
is
generated
in
the
least
significant
byte
of
the
result
field.
The
sign
(rightmost
four
bits
of
the
result
operand)
is
aC16
(1100)2
for
a
positive
field
or
a
D16
(1101
2
)
if
the
result
field
is
negat,ive.
The
Condition
Code
Indicator
is
set
following
execu-
tion
of
the
instruction
based
on
whether
the
result
field
is
zero,
positive
(greater
than
zero),
negative
(less
than
zero),
or
if
overflow
has
occurred.
Over-
flow
interrupt
can
occur
after
add
and
subtract
oper-
ation,
but
not
after
multiply
or
divide.
Overflow,
if
present,
overrides
the
setting
for
a
positive
or
neg-
ative
result.
As
an
example,
assume
the
following
fields
are
in
memory:
BAL
I
06
I
07
08
09
50
23
I
87
23
1+
I
(
\
AMT
51
50
51
52
)
23
47
5+
and
the
following
instruction
is
issued:
ASSEMBLY
OPERATION
OPERAND
INSTRUCTION
AP
BAL(3),
AMT(3)
OP
Ll
L2
Bl
Dl
B2
D2
GENERATED
I
FA
16
12
I
2
1
210
1
091110
1
210
1105410
I
INSTRUCTION
General
Register
two
contains
4096
10
29
the
result
field
will
appear
and
the
Condition
Code
Indicator
will
be
set
as
follows:
BAL
06
:
07
08
09
50
23
:
10
70
6+
CONDITION
CODE
=
3
(overflow)
When
overflow
occurs,
the
position
to
the
left
of
the
result
field
(HSM
5006
above)
is
not
affected
by
the
1
carry
out
of
the
MSD
of
the
result.
The
overflow
setting
(Condition
Code
3)
overrides
the
positive
result
setting
which
would
otherwise
be
set
(Condi-
tion
Code
2).
The
operands
being
added
(or
subtracted)
do
not
have
to
be
of
equal
length.
The
first
(and
result)
operand,
however,
should
be
the
longer
operand
if
they
are
unequal.
The
first
operand
can
be
considered
the
controlling
operand.
If
the
second
operand
is
shorter
in
length,
high-
order
zeros
are
generated
by
hardware
until
the
leftmost
digit
of
the
first
operand
has
been
reached.
If
the
second
operand
is
longer,
its
high-order
ex-
cess
bytes
do
not
affect
the
result.
It
should
be
noted
that
this
condition
does
not
neces-
sarily
set
the
overflow
condition.
Overflow
is
set
only
by
a
1
carry
from
the
most
Significant
digit
of
the
result.
For
example,
assume
HSM
contains
a
field
with
the
following
value:
BAL
00
01
02
30
75
23
4+
and
an
Amount
field
contained
the
following
values:
EXAMPLE
1
EXAMPLE
2
AMT
AMT
20
21
22
23
24
)
20
21
22
23
24/
30
5+
)
30
00
05
21
67
00
03
31
84
2+,
\
34
36
Table of Contents
Table of Contents
4
General Description
7
High-Speed Memory
9
Introduction
9
HSM Addressing
9
Hexadecimal Numbering System
10
Exercise
11
Data and Instruction Format
12
Data Formats
12
Unpacked Format
12
Edited Format
12
Machine Instruction Format
13
Exercise
13
Interrupt
15
Introduction
15
Programming States
15
Processing State
15
Interrupt State
15
Types of Interrupt
15
I/O Interrupt
15
Operation Code Trap
16
Arithmetic Overflow and Divide Exception
16
Elapsed Timer Interrupt
17
Inhibiting Interrupt
17
Exercise
17
Summary of Interrupt Logic
18
Elapsed Time Clock
19
Introduction to the RCA 70/25 Assembly Language
20
Format Requirements
20
Addressing
20
Self-Defining Values
22
Expressions
22
Implied Lengths
23
Assembler Controlling Codes
23
Define Storage (DS)
24
Origin Code (ORG)
24
Constant Definition (DC)
24
Program Linking Codes (ENTRY and EXTRH)
25
Run and Segment Controlling Codes (START, END, CSECT)
26
Equate Code (EQU)
27
Base Register Controlling Codes (USING, DROP)
27
Extended Mnemonic Instructions
27
Exercise
28
Instruction Complement
30
Data Movement Instructions
30
Move Character (MVC)
30
Exercises
31
Packing and Unpacking Data (PACK and UNPK)
32
Exercises
33
Decimal Arithmetic Instructions
35
Decimal Add (AP) and Subtract (SP)
35
Decimal Multiply (MP)
36
Decimal Divide (DP)
37
Exercises
37
Data Editing Instruction (ED)
39
Examples
40
Exercises
41
Comparison and Branching Instructions
43
Compare Logical (C LC)
43
Compare Decimal (CP)
43
Branch on Condition (BC)
44
Branch and Link (BAL)
44
Branch on Count (BCT)
45
Set P2 Register (STP2)
45
Exercises
45
Load and Store Instructions
47
Load Multiple (LM)
47
Store Multiple (STM)
47
Binary Arithmetic Instructions
48
Binary Add (AB) and Subtract (SB)
48
Exercise
48
Logical Instructions
51
Logical and (NC)
51
Logical or (OC)
51
Exclusive or (XC)
51
Use of Logicals
52
Test under Mask Instruction (TM)
53
Data Translation, Translate (TR)
53
Inputloutput
55
Introduction
55
Read Instructions (RDF) and (RDR)
55
Writing Data (WR) and (WRE)
56
Controlling Peripheral Devices
56
Error Recognition
57
Logic
59
Standard Device Byte
59
Sensing Exceptional Conditions
59
Peripheral Unit Sense Bytes
60
Summary of 1/0 Logic
61
Example of 110 Coding
62
Exercise
63
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Reference Manual
260 pages
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RCA Spectra 70 Specifications
General
Manufacturer
RCA
Model
Spectra 70
Category
Computer Hardware
Word Size
32 bits
Memory
Up to 512 KB
Predecessor
RCA 3301
Successor
RCA Series
Related product manuals
RCA 70/46
260 pages