EMERSON KJ4001X1-BA1功率控制器
POST映像應(yīng)返回到引導(dǎo)加載程序，但不是必需的。返回后，引導(dǎo)加載程序繼續(xù)掃描可執(zhí)行的備用引導(dǎo)映像。將控制權(quán)返回到引導(dǎo)加載程序的POST映像必須確保在返回時，板的狀態(tài)與POST進入時板的狀態(tài)一致。USER映像不應(yīng)將控制權(quán)返回到引導(dǎo)加載程序。6.7.5備用啟動映像和安全啟動MOTLoad的一些較新版本支持備用啟動映像以及安全啟動恢復(fù)過程。如果MVME7100上有安全啟動，則支持備用啟動映像。在支持備用引導(dǎo)映像的情況下，引導(dǎo)塊中的引導(dǎo)加載程序代碼檢查閃存庫的上8MB以查找備用引導(dǎo)映像。如果找到映像，則將控制權(quán)傳遞給映像。引導(dǎo)映像固件掃描通過檢查每個1MB邊界的一組定義的標(biāo)志來執(zhí)行掃描，這些標(biāo)志將映像標(biāo)識為POST、USER或備用MOTLoad。POST是用戶開發(fā)的開機自檢，它將執(zhí)行一組診斷，然后返回引導(dǎo)加載程序映像。USER將是一個引導(dǎo)映像，例如VxWorks bootrom，它將執(zhí)行板初始化?？梢龑?dǎo)的VxWorks內(nèi)核也可以是USER映像。引導(dǎo)映像的大小不限于1MB或更?。蝗欢?，它們必須從掃描閃存庫8MB內(nèi)的1MB邊界開始。
POST images are expected, but not required, to return to the boot loader. Upon return, the
boot loader proceeds with the scan for an executable alternate boot image. POST images
that return control to the boot loader must ensure that upon return, the state of the board is
consistent with the state that the board was in at POST entry. USER images should not
return control to the boot loader.
6.7.5 Alternate Boot Images and Safe Start
Some later versions of MOTLoad support alternate boot images and a safe start recovery
procedure. If safe start is available on the MVME7100, alternate boot images are
supported. With alternate boot image support, the boot loader code in the boot block
examines the upper 8MB of the flash bank for alternate boot images. If an image is found,
control is passed to the image.Boot Image Firmware Scan
The scan is performed by examining each 1MB boundary for a defined set of flags that
identify the image as being POST, USER, or Alternate MOTLoad. POST is a userdeveloped Power On Self Test that would perform a set of diagnostics and then return to
the boot loader image. USER would be a boot image, such as the VxWorks bootrom, which
would perform board initialization. A bootable VxWorks kernel would also be a USER
image. Boot images are not restricted to being 1MB or less in size; however, they must
begin on a 1MB boundary within the 8MB of the scanned flash bank.
