ARM Generic Timer

1. 調度 Event

2. 根據counter value，觸發(fā)中斷

3. 支持Virtualization 擴展

Generic Timer提供的system counter:

(1) 最少56bit 寬

(2) Frequency : 1--50MHz

Supports one or more alternative operating mode in which it increments by larger amounts at a lower freqency

(typically for power-saving)

(3) Roll-over : 至少40年，才會(huì )發(fā)生

(4) 精度: ARM本身不規定，但建議24小時(shí)內，誤差不超過(guò)10秒

(5) Start-up : 從0開(kāi)始計數