RCA 301, Руководство программиста

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In most cases, the entire A address refers to a HSM location, and the entire B address refers to another HSM
location. In some instructions, however, only a portion of the A address or B address is used, or one part of the
address may designate one value and the other part another value. The components of the A address are referred
to as A
n
, A
15
A
2
, A,, and the components of the B address as B„, B„ B,, B
3
.
In instructions where the N character is used as a count, the number of the count may be from 0 to 44. As the
N character can only contain one character, the following symbols are used to designate the N character for counts
from 0 to 44:
N Count Symbol N Count Symbol
N Count Symbol N Count Symbol
0 0 11 A 22 K
33 T
1
1 12 B
23 L 34 U
2 2
13 C 24 M
35
V
3 3
14
D 25
N 36
W
4 4
15 E 26 O
37 X
5 5 16 F
27 P
38
Y
6
6 17 G
28
Q
39
Z
7
7 18
H 29 R
40 EB
8
8 19 I
30
»>
41 , (comma)
9 9 20 — ( minus)
31
/
42 %
10
& 21 J
32 S
43
• (ISS)
44
=
Storage of Instructions
Instructions are stored sequentially in the High Speed Memory. Each instruction is stored in ten consecutive
memory locations (5 diads) so that the Operation Code is placed in the first character of a diad.
Staticizing
An instruction can be interpreted and executed by Program Control only after it has been brought out of the
High Speed Memory locations in which it has been stored, and its components placed in the proper registers. This
process is called "staticizing" and is accomplished in five status levels.
A status level lasts for seven microseconds and is a term applied to a series of pulses which open certain paths
over which information can travel. Each status level has a specific function. In staticizing each instruction, the first
status level brings the first diad (two characters) of the ten character instruction (ONAAAABBBB) into the
Memory Register and automatically regenerates the characters in their original location in the HSM.
The O character is then sent to the NOR Register, and the N is sent to the N Register. This completes the
first status level. The^ second status level brings the next diad (A
0
, A,) into the memory register, regenerates the
characters, and sends the A
0
, A, characters to the A Register. During the third status level the A
2
, A
3
characters
are transferred in a similar manner, and the fourth and fifth status levels transfer B
0
, Bj and B
2
, B
3
to the B Address
Register.
The total staticizing time is 35 micrbseconds, and is constant for every instruction, even when the N count is
zero. The number of status levels involved, and their sequence for execution (after staticizing) of a given instruction,
depends upon what must be accomplished by that instruction.
Direct and Indirect Addressing
When the least significant character of an address is written as a number, i.e., the zone bits are 00, the address
is a direct address. Direct addresses establish the initial register settings for instructions in which they are employed.
III-2