RCA 301 Programmer's Reference Manual page 67

When the SUBTRACT instruction is used for address modification, the following special conditions apply:
1. If an indirect address is indicated by a one in the 2
generated in the 2
2. Both addresses entering the subtraction must be positive.
3. The result must be positive.
Final Register Contents
(A) = Address of location one to the left of the MSD of the difference.
r
(B) = Address of location one to the left of the MSD of the subtrahend.
f
PRI
PRP is set if the result is positive.
PRZ is set if the result is zero.
PRN is set if the result is negative.
Timing
Total time in microseconds
= 28n 49, where n is the number of characters in either operand (operands must be of equal lengths).
-T
If an "end around condition" exists, 2In + 14 microseconds must be added to the above.
Example
Instruction:
Operation
—
HSM before Instruction is Executed:
2001 2002 2003
A E R
HSM after Instruction is Executed:
2001 2002 2003
A E R
Final Register Contents:
(A), = 2003
(B), = 2007
PRI
PRP is set
Time:
28 (3) + 49 = 133 gs.
J position of the LSD of the difference.
N
3
2004 2005
9
9
2004 2005
8 7
4
bit position of the LSD of either operand, a one is
A Address
2006
2007 2008
2006
1
3
9
2006 2007 2008
6 1
3
B Address
2010
2009 2010
2
3
2009 2010
2 3
VI-7