5.26. Subtract One and Jump


Addr
Mode  Mnemonic          Format/Opcode
                           8      4      4             16
D     SOJ   RA,LABEL    --------------------------------------
DX    SOJ   RA,LABEL,RX |  73  |  RA  |  RX  |  |   LABEL    |
                        --------------------------------------

Description. The 16 bit contents of register RA are decremented by one. Then if the content of register RA is zero, the next sequential instruction is executed. If the content of register RA is non-zero, then a jump to the Derived Address, DA, occurs.

Note: If RA = RX, then the derived address, DA, is calculated before RA is decremented.

Register Transfer Description.

(RA) <-- (RA) - 1;
(IC) <-- DA if (RA) /= 0;
(CS) <-- 0010  if (RA) = 0;
(CS) <-- 0001  if (RA) < 0;
(CS) <-- 0100  if (RA) >= 0;

Registers Affected. RA, CS, IC (if the jump is executed)