video armv7 timer
Questions about Generic Timer in ARMv8 - Arm Community
In ARM V7 RM, I saw "This chapter describes the implementation of the ARM Generic Timer as an OPTIONAL extension to an ARMv7-A or ARMv7-R processor implementation. So, I think it means that a SoC implementation can choice to involve the system timer or not.
How to initialize the core Timer in an ARM Cortex-A7
The ARM Generic Timers (henceforth, "GT") are architecturally specified in ARMv7 as an OPTIONAL extension to the ARMv7-a and ARMv7-r streams. The feature is specified to provide a system-wide timestamp-counter (henceforth, "syscounter") reference which operates independent of the CPU clock's frequency, allowing for TSC measurements which are ...
Documentation - Arm Developer
Armv7-M: System Tick Timer. The System Tick Timer (SysTick) dialog (for Cortex-M3, Cortex-M4, and Cortex-M7 cores) shows controls for the system timer. The system timer is an optional feature. If not implemented, then the SysTick registers are reserved.
PDF ARMv7 Quick Reference - University of Washington
Timer其实就是定时器，它可以定义一段指定的时间，当时间到了，就会assert一个外部的输出信号（可以输出到GIC，作为一个interrupt source）。 从power domain来看，ARM generic timer分成两个部分：System counter和各个Multiprocessor系统中的Timer_x、接口电路等。 之所以这么分原因很明显：功耗方面（电源管理）的考量。 在power saving mode下，可以shutdown各个processor系统的供电，但是可以保持system counter的供电，这样，至少系统时间可以保持住。