TMS320F280049: QCTMRLAT equal to 0 & QCPRDLAT != 0 & while the UPEVNT triggered at low speed

Part Number: TMS320F280049

Hi Team,

  My customer reported an issue for QCTMRLAT = 0 unexpected while in QCLM = 0. At the same time QCPRDLAT is same as previous period(not updated). While using the T-algorithm to calculate the speed, it got a very higher speed and the stepper motor reported voice noise, 

The ISR frequency is 20Khz which read the QPOSCNT, and the Encoder feedback frequency is also 20Khz, and update the QCTMRLAT & QCPRDLAT while read the QPOSCNT.

  Searched the E2E which reported an similar issue.

https://e2e.ti.com/support/microcontrollers/c2000/f/171/p/688726/2565235?tisearch=e2e-sitesearch&keymatch=eQEP%2520QCTMRLAT#2565235

Supports Need:

1. Workaround for how to avoid the QCTMRLAT updated with 0 issue asynchronous updated while UPEVNT triggered?

2. Could BU kindly give comments for why UPEVNT and QCTMRLAT & QCPRDLAT not updated synchronous while in some boundary situation as upper link?