Andes Workshop http://forum.andestech.com/ |
|
STANDBY指令 http://forum.andestech.com/viewtopic.php?f=14&t=62 |
Page 1 of 1 |
Author: | infinity [ Wed Apr 20, 2011 10:37 am ] |
Post subject: | STANDBY指令 |
這個指令可以使cpu進入待機模式,能節省電力, 在AndeStart_ISA_UM025_V1.4.pdf裡面有說明。 節錄如下: Attachment: Syntax: STANDBY SubType (= no_wake_grant, wake_grant) Purpose: It is used for a core to enter a standby state while waiting for external events to happen. Description: This instruction puts the core and its associating structures into an implementation-dependent low power standby mode where the instruction execution stops and most of the pipeline clocks can be disabled. The core has to enter the standby mode after all external memory and I/O accesses have been completed. In general, the core leaves the standby mode when an external event happens that needs the core’s attention. However, to facilitate the need for an external power manager to control the clock frequency and voltage, the wakeup action may need the external power manager’s consent. Thus two flavors of STANDBY instruction are defined to distinguish the different usages. The SubType field definitions are listed as follows. (點選圖片可以放大顯示) Attachment: Attachment: pp3.gif [ 10.5 KiB | Viewed 15189 times ] The wakeup external events include interrupt (regardless of masking condition), debug request, wakeup signal, reset etc. And the instruction execution restarts either from the instruction following the STANDBY instruction or from the enabled interrupt handler which cause the core to leave the standby mode. When entering an interrupt handler, the IPC system register will have the address of the instruction following the STANDBY instruction. An implementation can export the standby state to an external agent such as a power/energy controller to further regulate the clock or the voltage of the processor core for maximum energy savings. However, if any such clock or voltage regulation causes any core/memory state loss, software is responsible to preserve the needed states before the core enters standby mode. And if such state loss has happened, the only sensible way to bring the core into action is through a reset event. 沒有全部貼上來,看文件比較清楚。 |
Page 1 of 1 | All times are UTC + 8 hours [ DST ] |
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |