6502 IRQ during reset

From: Istvan Hegedus <*hegedusishe_at_gmail.com*> Date: Tue, 5 Mar 2019 21:35:52 +0100 Message-ID: <CAJG-dDTgETKjvcKdBwcD=hnO4sgviKjepWLcy-bNAgvGqrP9rg@mail.gmail.com> · hegedusishe_at_gmail.com

Hi All,

I have created a kernal switching kernal for my FPGA plus4 implementation
and faced an issue during switching kernals. I don't want to go into too
much details but my romconfig kernal initiates a hardware reset after
configuring the proper roms (also kernal itself) but after RESET line of
the CPU goes high (inactive) there is always an interrupt generated because
the IRQ line is low. It seems the FPGA 6502 cores don't set the I flag to
high during reset, I have tried 2 cores, T65 and FPGA64 project's core but
both behaves nearly the same. The 6502 datasheet says that Interrupt flag
is set after/during reset . Is it the CPU implementation wrong or it should
really behave like this?
One thing is sure, after power up these cores have the I flag set but RESET
does not affect the flag.
Thanks
Istvan