Timing question for kuroneko

Cluso99

kuroneko: As the resident expert, i wanted to ask how to best do the following....

I want to generate a clock output with 4 clocks high and 4 clocks low. That is easy enough. Now, I need to have the cog exactly timed to increment a group of output pins (being used to increment an sram address) 2 clocks after the output clock pin goes high. With internal prop timings I may need to make this 1 or 3, but itwill be fixed.

What I am trying to do is log 8 data pins into sram every 8 prop clocks (512KB samples) triggered by a sequence of events.

So the cog once running will be in a 2 instruction loop, being add and djnz.

What I anticipate doing is to inc phsa each 4 clocks withfrqa=$2000-0000. I presume to get the clock offset I will preset phsa. Am I on the right track?

Cluso99

having problems fixing error with my xoom. Should be $4000-0000

kuroneko

Cluso99 wrote: »

What I anticipate doing is to inc phsa each 4 clocks withfrqa=$2000-0000. I presume to get the clock offset I will preset phsa. Am I on the right track?

Sounds about right. The preset entirely depends on how your code looks like (for 10MHz you want to keep activation closer to the loop), e.g.

movi    ctra, #%0_00100_000     ' NCO
movi    frqa, #%0010_00000      ' 10MHz

add     A, B
djnz    C, #$-1

The first active counter increment (phsx += frqx) happens during the first cycle of add_S. So the clock (assuming phsx starts with 0) goes high during add_R which is also when the result of add is written (i.e. becomes active). Which means you'd have to preload phsx with e.g. 2*frqx ($4000_0000, 2 cycles later $8000_0000).