STPM34 problems with phase-angle measurement

Hello. I'm working with stpm34 and have a next problem. I can't get phase-angle measurement. It's always zero. I've got period measurement and it work well. I checked PER_ERR, but it's odd. It's placed in two positions. First, in DSP SR, and there always 1. Second, in DSP LE, and there always 0. I just can't understand how it must work, please help.