Re: How-to predict pending dummy read of 6502 CPU?

From: Michal Pleban <*lists_at_michau.name*> Date: Fri, 13 Oct 2023 17:31:22 +0200 Message-ID: <d6a485c8-bb8d-79aa-3d67-76b3deae82ed_at_michau.name> · lists_at_michau.name

Hello!

Frank Wolf wrote on 13.10.2023 13:30:

> Is there any easy way to detect or predict a dummy read? Maybe when 
> looking at some internal signals

You can look at the SYNC signal, which indicates an opcode fetch. 
Knowing the opcode, you know which instruction is being executed, and 
based on that you know which cycle after the SYNC cycle is a dummy read.

There use to be a hardware device that used this technique, but its Web 
page does not work anymore :(
http://homepage.mac.com/jorgechamorro/a2things/a2gratisDMA/

Regards,
Michau.