RCA 301 Programmer's Reference Manual page 83

X Tally (TA)
General Description
This instruction permits looping through a sequence of operations by automatically reducing a pre-stored
quantity each time control is transferred to the beginning of the sequence. When the quantity (always a positive
numeric) has been exhausted, the Tally ends and the instruction following it is performed. The maximum value of
of Tally quantity is 99.
Format
Operation — X
N —0 (Zero)
A Address — HSM address of the diad containing the quantity to be tested.
B Address — HSM location of next instruction to be performed if quantity being tested has not been exhausted.
Outline of Operation
The contents of the HSM diad specified by the A Register are transferred to the D Register. If the quantity is
00, the Tally ends and the next instruction in sequence is executed. If the quantity is other than 00, the contents
of the D Register are decremented by one and stored in the HSM diad location specified by the A Register. The
contents of the P Register are stored in STP, and the contents of the B Register are transferred to the P Register.
Final Register Contents
(A), = (A),
(B)r = (B),
Timing
70 jus — When Tally quantity is greater than zero upon starting.
49 fxs — W hen Tally quantity is equal to zero upon starting.
Standard Location
STP (on transfer only)
VII-9