RCA 301 Programmer's Reference Manual page 141

F Block Read Record Normal (BRN)
General Description
This instruction reads from a selected cell of the Data Record File to a designated HSM location. From one
to ten blocks of information may be transferred from the Data Record File with one instruction. A cell may contain
a block of one to 900 characters of information to be transferred. In reading, the end of the block of information
is designated by an EB symbol, or a count of 900 characters in the cell.
Format
Operation — F
N Selects the Data Record File Unit and number of blocks to be read as indicated below:
Number of Blocks
to be Read
First File
Second File
A Address — HSM address where first character is to be placed.
B Address — B must be zero (0).
0
B, determines if record stays on turntable after operation.
B, = odd — record returned to cage.
Bj = even — record stays on turntable and arm is placed at beginning of previously selected
band.
B specifies whether EB is sensed or not.
2
B = 1 — block is terminated on counting of 900 characters.
2
B = 0 — count or EB recognition.
2
If EB sensed before 900 characters have been read, stop transfer from this cell. If
900 count reached before an EB sensed, stop transfer from this cell.
B addresses cells 1 through 10, with cell 1 specified by zero and cell 10 specified by 9-
3
Direction of Operation
Left to right in HSM.
Outline of Operation
A start signal is sent to the Data Record File and the read-write head is placed on the record on the turntable.
The contents of the cell specified in B
location designated by the A Register. Transfer is accomplished one character at a time, with the contents of the
A Register being incremented by one after each character transferred. When the end of a block is reached, determined
by B , N is decreased by one. When N is decreased to zero the operation terminates. The record does not have to be
2
returned to the cage to perform additional read or write instructions from the same surface.
Final Register Contents
(A) = Address of HSM location one to the right of the last character put in memory.
t
(B)t = (B)
t
2 4
1 3
4
2 3
1
D
C
A B
Standard Location
STA (0212 - 0215)
are transferred to the Record File Buffer and from the buffer to the HSM
3
7 8
6
5
8
6 7
5
G H
E F
10
9
0
9
I &
XI-7