tops20 assembly tutorials

David Bridgham dab at
Tue Mar 8 16:52:25 CST 2016

On 03/08/2016 05:47 PM, Phil Budne wrote:
> CIRC is an MIT/ITS instruction; ISTR a flavor of "rotate"

It's a double-word rotate like ROTC except the two registers rotate in
opposite directions.  The instruction

    CIRC  AC, 36.

will swap AC and AC+1 and reverse both of their bit orders.

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