Specifications

Deferred register addressing may also

selected in

PAL-11

by the form

OPR (R).

INDEXED AD~RE&G-T~IZ general fegisters may be used as index reg

jr&en to per&t random access of items in tables or stacks of data.

InStrUC-

tions of the form

OPR X(R)

specify indexed mode addressing. The effective address is the sum of X

and the contents of the specified general- register R.

The index word containing X follows the instructi& word.

Index mode addressing can be deferred to permit access of data elements

through tables or stacks of their addresses. The address field for index de-

ferred mode is

It is specified by instructions of the form

OPR @X(R) _

AUTOINCREMENT ADDRESSlNCiAutoincrement addressing provides for

automatic stepping of a pointer

through sequential elements of a table

of operands. In this mode, the address of the operand is taken from the

general register and then the contents of the register are stepped (incre-

mented by one or two) to address/the next word or byte depending upon

whether the instruction operates on byte or word data. Instructions of the

form

01% (RI+

specify autoincrement addressing. The address field for autoincrement ad-

dressing is

This mode may also be deferred. Instructions of the form

OPR @(Wk

specify deferred autoincrement addressing and assemble with the followihg

address field.

AUTODECREMENT ADDRESSlN*Autode&ement addressing steps the spe-

cified general register to the next lower byte (decrement by one) or word