From the datasheet -
SyncMode – Resamples (single-synched) the control bit input from the bus clock to the
selected SC clock before it is driven into the routing.
This mode syncs the value you write to the bit in the control reg. For those applications
which require deterministic control.
PulseMode – This mode is similar to SyncMode, in that the Control bit input is resampled
from the bus clock to the selected SC clock and a single SC clock period pulse is generated.
The output of the control bit into the routing is asserted for one full SC clock period. At the
end of the pulse, the control bit is automatically reset.
In short when you write a "1" to a bit in the control reg the output, instead of going to a "1"
and staying there will go to a 1 for 1 clock period, then is automatically reset back to a "0"
Sync mode allows you to sync the written data to a clock that is not the internal bus clock. That way you can ensure that changes to the output happen only at specific moments. E.g. you drive a parallel bus, whose clock is external. Then you route this clock to the clock input of the register, and set sync mode. Changes to the output then happen only then the external clock rises.
Pulse mode is similar, but the data on the outputs is valid only for a single clock period. You can use that to create pulses of a specific widht (that of the external clock), that are synced with this external clock.
Sync mode allows you to sync the written data to a clock that is not the internal bus clock
You can also synch to the buss clock.
@dana: I thought that outputs to the control register is synced to the bus clock anyway. At least I understood the data sheet that way (its even in the part you quoted).
For pulse mode it might make sense though.
Looks like in all cases buss clock is used to resample input,
so I agree no need in any mode to supply clock as buss clock.
I think the default clock for control register is bus clock. Hence if no external clock is provided, data is synced to bus clock. Now it makes sense. Thanks a lot guys for your help :)