RCA 301, Programmer'S Reference Manual

Page: 153 / 235

S Input/Output Sense (IOS)
General Description
This instruction tests the desired status of the selected Data Record File and chooses one of two sequences of
instructions.
Format
Operation —S
N — Selects the Data Record File to be tested according to the following:
Device
N
Device
Unit #1 Unit #2
Data Record File (under control of DRFC Unit)
1
R
Z
Data Record File (under DRFM Control Unit)
Note #1: Data Disc File #1 prohibits the inclusion of Data Record File #1 operated through the DRFC.
Data Disc File #2 prohibits the inclusion of Data Record File #2 operated through the DRFC.
A Address — A
0
specifies the tests to be performed as follows:
"1" Bit
in
Numeric
Equivalent
Tests
2°
1
Is the selected device inoperable?
2
1
2
Is the selected device reading or writing?
2
2
4
Is a record on the turntable of the selected Data Record File?
— A
a
, A
2
, A
3
— Must be zeros (000).
B Address — HSM location of the next instruction to be executed if the condition or conditions being tested
are present
Standard Location
STP (on transfer only)
Outline of Operation
The test (or tests) called for by the one bits in A
0
are performed on the device selected by N. If any one of
the conditions is present, the contents of the P Register are transferred to STP and the contents of the B Register
are then transferred to the P Register. If no tested condition is present, the next instruction in sequence will be
executed.
Final Register Contents
(A)
f
= (A),
(B)t = (B)i
Timing
56 jus if a transfer is executed.
42 p,s i f no transfer takes place.
XI-19