Originally Posted by
Edison4
philba,
As you mentioned, I'm relying on the schmitt triggers to provide some noise immunity. A low pass filter with the wrong cutoff could accidentally limit the step rate.
About the sync signal: The first part of the data sheet is pretty clear - SYNC should be low when CLOCK input is active (high) and should go high when the CLOCK signal has been low (after a time delay). My circuit follows these rules & works just fine.
The confusion with the sync signal comes from the following: "NOTE - The use of this function except at 0, 70.7, or 100% Itripmax (half-step positions 0 through 8) is not recommended."
After much contemplation on that sentence, I have decided that what it means is:
CONTINUOUS synchronization operation (a logic high on sync input) is not recommended during normal stepping (except at 0, 70.7, or 100% Itripmax). That is why the data sheet is suggesting that the additional circuitry should be used to switch the synchronous mode on and off.
DW