Unfortunately, the timer expired signal functionality is not available for ADSP-SC5xx and ADSP-215xx processor.
It supports legacy SHARC processor, the FLAG3 pin can act as a core FLAG3 or the TMREXP signal of the core timer or as a memory select MS3. If the FLAG3 pin is configured as TMREXP, when the TCOUNT value reaches zero, the timer generates an interrupt and asserts the TMREXP output pin high for several cycles (when the timer is enabled).