EMERSON KJ4001X1-BA1功率控制器
POST映像应返回到引导加载程序，但不是必需的。返回后，引导加载程序继续扫描可执行的备用引导映像。将控制权返回到引导加载程序的POST映像必须确保在返回时，板的状态与POST进入时板的状态一致。USER映像不应将控制权返回到引导加载程序。6.7.5备用启动映像和安全启动MOTLoad的一些较新版本支持备用启动映像以及安全启动恢复过程。如果MVME7100上有安全启动，则支持备用启动映像。在支持备用引导映像的情况下，引导块中的引导加载程序代码检查闪存库的上8MB以查找备用引导映像。如果找到映像，则将控制权传递给映像。引导映像固件扫描通过检查每个1MB边界的一组定义的标志来执行扫描，这些标志将映像标识为POST、USER或备用MOTLoad。POST是用户开发的开机自检，它将执行一组诊断，然后返回引导加载程序映像。USER将是一个引导映像，例如VxWorks bootrom，它将执行板初始化。可引导的VxWorks内核也可以是USER映像。引导映像的大小不限于1MB或更小；然而，它们必须从扫描闪存库8MB内的1MB边界开始。
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.
