[Coco] Indexed addressing postbyte

[jdaggett at gate.net]

James 

In the 6809 the last four bits are decoded as an opcode. Bit 4 tells 
the processor either indexed and indirect indexed mode. 

james

On 8 Aug 2004 at 21:30, James Dessart wrote:

From:           	James Dessart <james at skwirl.ca>
Subject:        	Re: [Coco] Indexed addressing postbyte
Date sent:      	Sun, 8 Aug 2004 21:30:35 -0400
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> 

> On 8-Aug-04, at 9:24 PM, Robert Gault wrote:

> 

> > Note that bits 5&6 determine the register and the other bits

> > determine the function. There may be other bytes after the postbyte

> > as needed for addresses.

> 

> If that's how they're being numbered, reverse my numbers then. :) I

> always speak in most-significant-bit. :) with 1 as my starting index.

> :) darn that pre-Arabic ordinal numbering habit! :)

> 

> James

> 

> 

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