RCA 301, Programmer'S Reference Manual

Page: 139 / 235

E Band Select Record File Mode (BSM)
General Description
This instruction initiates a search of a designated Data Record File for the record containing a specified band,
places the record on the turntable and advances the read/write arm to the "ready" position. Once this instruction
is initiated (staticizing and establishing a control counter), the data record and band are selected independent of
computer operation.
A Band Select Record File Mode instruction must be issued prior to a Record File Mode Read (or Write)
instruction (RMR, RMW). These instructions may be used to address one of four Data Record Files controlled
through the Data Record File Mode Control.
Format
Operation —E
N — Selects the Data Record File Unit and Band as indicated below:
Data Record File Unit
Effect
1 2
3 4
Effect
0 &
> » The record on the turntable, if any, will be returned to the cage. The
desired record is then placed on the turntable and the indicated band
selected.
1 A
J
/
The band selected is one of the two on the upside of the disc on the
turntable. If the B address is even, the first band will be selected; if odd,
the second band will be selected.
A Address — Must be zeros (0000).
B Address — B
0
must be zero (0); B
3
, B
2
, and B, designate band (000 to 511).
Outline of Operation
Band addresses are numbered from 000 through 511, and are specified by the last three digits
The contents of the N Register designate the proper Record File and specify whether the record
if any, is to be returned to the cage or not.
Final Register Contents
(A)
f
= (A);
(B)f = (B)i
Timing
A. Computer time to initiate selection (staticizing + establishing address
+ 14 (B
2
) + 42.
B. Select data record from storage wheel:
Note: Since the 128 position data record storage wheel rotates in either
position from the selection point is 64.
of the B address,
on the turntable,
counter) in microseconds: 21 (B
3
)
direction, the maximum data record
XI-5