MC6821

[K2LRV]

Anyone out there have experience with an MC6821?

I am working on an upgrade project and the existing circuit uses this
chip. I specifically need to determing how the IRQ lines get set
active.

Thanks,

 

[James Beck]

In article <b9950a9e-747a-43f8-bdce-18565f864fa2
@m3g2000hsc.googlegroups.com>, lou002@gmail.com says...

Anyone out there have experience with an MC6821?

I am working on an upgrade project and the existing circuit uses this
chip. I specifically need to determing how the IRQ lines get set
active.

Thanks,


http://www.datasheetcatalog.com/datasheets_pdf/M/C/6/8/MC6821.shtml

 

[James Beck]

In article <7384c8b0-7d42-4312-9bd5-0682b2c130e7
@z18g2000prn.googlegroups.com>, lou002@gmail.com says...

On Oct 17, 10:22 am, James Beck <j...@reallykillersystems.com> wrote:
In article <b9950a9e-747a-43f8-bdce-18565f864fa2
@m3g2000hsc.googlegroups.com>, lou...@gmail.com says...> Anyone out there have experience with an MC6821?

I am working on an upgrade project and the existing circuit uses this
chip.  I specifically need to determing how the IRQ lines get set
active.

Thanks,

http://www.datasheetcatalog.com/datasheets_pdf/M/C/6/8/MC6821.shtml

Thanks, but I have the data sheet, I just do not quite understand how
the IRQ flag sets set... From readind the data sheet it appears as if
the flag can be set when there is a read from a specific address, but
I cannot seen to actually see this happening on a logic analyzer...

No, page 8 has the information you are looking for.

The interrupt is RESET when you read the peripheral data section.

The flags can not be set through the MPU data bus.
They can only be set by transitions on the CA and CB peripheral control
pins.

Look at the information about the control register.
You have to set the CA/CB pins up to generate interrupts on a H to L or
L to H transition and then enable the interrupt.

 

[K2LRV]

On Oct 17, 10:22 am, James Beck <j...@reallykillersystems.com> wrote:

In article <b9950a9e-747a-43f8-bdce-18565f864fa2
@m3g2000hsc.googlegroups.com>, lou...@gmail.com says...> Anyone out there have experience with an MC6821?

I am working on an upgrade project and the existing circuit uses this
chip.  I specifically need to determing how the IRQ lines get set
active.

Thanks,

http://www.datasheetcatalog.com/datasheets_pdf/M/C/6/8/MC6821.shtml

Thanks, but I have the data sheet, I just do not quite understand how
the IRQ flag sets set... From readind the data sheet it appears as if
the flag can be set when there is a read from a specific address, but
I cannot seen to actually see this happening on a logic analyzer...