nRF52 supports Systick timer. But I can not find information about it in the "nRF52832 Objective Product Product Specification". Is it currently open for user ?
It's a standard (and required) ARM Cortex M4 system component, all the details are in the ARMv7m documentation, just write the registers and use it.
ARM's documentation for the Cortex-M Systick can be found here. Additionally, the SDK now includes a systick driver. You can refer to the Blinky SysTick Example for how to use it.
You can use CMSIS functions for it.
I don't need a callback that is regularly triggered as SysTick_Handler().
I just want to know the system tick with granularity of us when needed. Is there a way other than using SysTick_Handler()?
The link is broken.