Sysref signal of hmc7044 is not controlled

Hello, the hmc7044 clock chip I used configures a channel as a sysref channel. It does not use SPI to write the reseeding and pulse generator request commands, but this channel outputs 16 sysref pulses with a frequency of 1.92mhz. The PLL1 and pll2 of the clock have been locked. What's the matter?