On Tue, 10 Feb 2026 at 23:21, Seymour J Metz <[email protected]> wrote:

> You can't have a negative displacement on an RS or RX instruction. It's a
> 12 bit unsigned field, padded with zeros on the left.


Sure - 12-bit displacements are unsigned, and addressing arithmetic using
them is unsigned. But the assembler can help you by allowing specification
of a negative number if there is a suitable USING in effect.

Off the top of my head, something like

LHI   R5,-1024
USING  -1024,R5

LA    R1,-123(R1)  Subtract 123 from R1

Tony H.

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