'H' in Illegal Opcodes?

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TylerBarnes
Posts: 15
Joined: Tue Mar 19, 2019 12:41 pm

'H' in Illegal Opcodes?

Post by TylerBarnes » Mon Feb 03, 2020 7:50 pm

Trying to understand some of the documentation out there regarding illegal opcodes. I cannot, however, figure out what the capital symbol 'H' is used for on this page for example: http://www.oxyron.de/html/opcodes02.html

My assumtion would be the high byte of the address. But it does not have a legend that explains this explicitly. Anyone care to shed some light?

AHX¹ {adr}:=A&X&H
SHY¹ {adr}:=Y&H
SHX¹ {adr}:=X&H
TAS¹ S:=A&X {adr}:=S&H

lidnariq
Posts: 9022
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: 'H' in Illegal Opcodes?

Post by lidnariq » Mon Feb 03, 2020 8:07 pm

Yes, that. H is the high byte of a 16-bit address.

edit: That said, SHY and SHX are not that simple.

Oziphantom
Posts: 785
Joined: Tue Feb 07, 2017 2:03 am

Re: 'H' in Illegal Opcodes?

Post by Oziphantom » Sat Feb 08, 2020 1:57 am

don't use the oxyron docs anymore, they are way out of date and not accurate.

Use https://csdb.dk/release/?id=185341 its the definitive source and has a lot more info.

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