[Oberon] Documentation;

Hellwig Geisse hellwig.geisse at mni.thm.de
Wed Dec 16 23:15:17 CET 2020

On Mi, 2020-12-16 at 12:55 -0800, peter at easthope.ca wrote:
> Section "1. Register instructions" mentions "... extended to 32 bits 
> with 16 v-bits to the left." What is a v-bit?

V is one of the modifier bits of instructions with format
F1:  01uv a b op im
       4  4 4  4 16
So it's bit 28.

Remark: It's a bit unusual to prescribe the bit value (0 or 1)
with which to extend the immediate constant instead of specifying
whether the constant will be sign- or zero-extended. This is
a trade-off: spend a bit in the opcode area and gain a bit
for a bigger constant range.

> mno = module number
> pno = program number

pno = procedure number (in the list of exported procedures
of the module mno)


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