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Advanced Programming
151
Using The I-Register For Display,
Storage Register, and Program Control
You have seen how the value in the I-register can be altered using (sT0],
(x=1], (1G], and
operations. But the value contained in the
I-register can also be used to control display, storage register, branching,
and subroutine operations. First, let's get a brief overview of these
operations. Then we'll examine each one in detail.
(osp1)(display I) uses a number stored in the I-register to specify the
number of decimal places appearing in the display.
(X exchange indirect) exchanges the contents of the displayed
X-register with the contents of the available storage register addressed
by the absolute value of the number in the I-register.
(1] (@](store indirect) stores the value that is in the display in the
storage register addressed by the absolute value of the number currently
in the I-register.
(7] [@](recall indirect) recalls the contents of the storage register
addressed by the absolute value of the number currently in the I-register.
(s70) ((#), x), (31, or (¥)) [w](indirect storage register arithmetic)
performs storage register arithmetic on the contents of the storage register
addressed by the absolute value of the number currently in the I-register.
[f] [1] (go to label or line I) with a positive number in the
I-register transfers execution of a running program sequentially down-
ward in program memory to the next label specified by the number
currently in I. With a negative number in the I-register, execution
transfers to the occupied line number specified by the absolute value of
the number currently in I.
(f] (1] (go to label or line I subroutine) with a positive number
in the I-register transfers execution of a running program sequentially
downward in program memory to the next label specified by the number
currently in I. With a negative number in the I-register, execution
transfers to the occupied line number specified by the absolute value of
the numbercurrently in I. In both cases, when a (RTn)is then encoun-
tered, execution transfers back to the line following the (GSB)instruc-
tion, and continues.
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