When does the AY reload its counters?

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When does the AY reload its counters?

Post by ThomH »

Suppose I've set the divider for channel 0 to be 1024, and there are 63 tone ticks — i.e. 1008µs — until the tone output next toggles. I then set the divider to 15. When should I expect the next change in output level?

Phrased differently: assuming a straightforward divider -> counter, counter -> zero implementation, when does the AY reload its tone counters? Possibilities:
  • only after reaching zero;
  • whenever a divider is set;
  • shortly after a divider is set;
  • only when the fine or coarse part of a divider is set;
  • some other time entirely.
Or does the assumption not hold up?

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Re: When does the AY reload its counters?

Post by Godzil »

I would say that the AY will re-get the values from the registers on each external clock edge.
What would probably happen is that the timer is not reset but will use the new parameters.

I think it can be tested by using maybe a slower clock (even if a sub 50Mhz scope would be enough) and do the test by setting the registers and watching the output.

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