RCA Spectra 70 Training Manual

It should be noted, based on the above example, that
with only two significant digits in the multiplier the
leftmost zero-filled byte in the product was not need-
ed. However, if the field NUNT contained three
significant digits the added zero byte would be re-
quired as in the following example:
Example #2
HSM BEFORE
EXECUTION
HSM BEFORE
AND AFTER
EXECUTION
ASSEMBLY l
INSTRUCTION
GENERATED
INSTRUCTION
HSM AFTER
EXECUTION
DIVIDE DECIMAL
22
22
22
WPRC
00
01 02
03
04
00
00
21
57
2+
30
31
87
5+
See Example 1 above
WPRC
00
01 02 03
04
01
88
75
50
0+
Division is performed on two packed operands with
the quotient and remainder replacing the first oper-
and (dividend) following execution of the instruction.
Two conditions cause a divide-exception interrupt
(assuming permit mask):
1. Dividend does not contain at least one signifi-
cant (leading) zero.
Example:
VALID
INVALID
5 BYTE
DIVIDEND FIELD
I 02 11 7 I 54 I 31 I 8+ I
112 11 7 I 54 I 31 I 8+ I
2. The divisor digits, when aligned with the digits
one position to the right of the leading zero of
the dividend, have a lesser or equal value.
31
Example:
I 01 I 751
42
1
1
+
I
DIVIDEND
VALID
1411 7+ I
DIVISOR
- - - -
1 01 I 751
42
1
1
+ I
DIVIDEND
INVALID
1
04
1
1
+ I
DIVISOR
A
divide-exception interrupt is avoided by position-
ing the dividend with sufficient leading zero digits.
For example, a two-byte divisor containing from one
to three Significant digits would not cause a divide
exception if two or more of the most significant bytes
of the dividend were zero.
Example:
HSM BEFORE
AND AFTER
EXECUTION
HSM BEFORE
EXECUTION
ASSEMBLY
INSTR UCTION
NAME OPERATION OPERAND
DP DIVD(4), DIVS(2)
~:S~~~~~~~N 1 FD \3
10
1110 I 2 1
0030
10 I 21000010 I
HSM AFTER
EXECUTION
General Register 2 = 2200
10
DIVD
Following the execution of a Divide instruction, the
remainder appears right justified in the dividend
field and is equal in length to the divisor. The length
of the quotient, therefore, is Ll - L2.
Exercise:
1. Assume HSM has been allocat ed as indicated on
Line 1 and that each location contains the values
as shown.

RCA Spectra 70 Specifications

General

Brand	RCA
Model	Spectra 70
Category	Computer Hardware
Language	English