Alternate Boot Data Structure; Alternate Boot Images And Safe Start; Boot Image Firmware Scan - SMART Embedded Computing MVME7100ET Installation And Use Manual

typedef struct altBootData {
unsigned int ramSize;/* board's RAM size in MB */
void flashPtr;/* ptr to this image in flash */
char boardType[16];/* name string, eg MVME7100 */
void globalData;/* 16K, zeroed, user defined */
unsigned int reserved[12];
} altBootData_t;
6.7.4

Alternate Boot Data Structure

The globalData field of the alternate boot data structure points to an area of RAM which
was initialized to zeroes by the boot loader. This area of RAM is not cleared by the boot
loader after execution of a POST image, or other alternate boot image, is executed. It is
intended to provide a user a mechanism to pass POST image results to subsequent boot
images.
The boot loader performs no other initialization of the board than that specified prior to the
transfer of control to either a POST, USER, or Alternate MOTLoad image. Alternate boot
images need to initialize the board to whatever state the image may further require for its
execution.
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 MVME7100ET, alternate boot images are
supported. With alternate boot image support, the boot loader code in the boot block
examines the upper 8 MB of the flash bank for alternate boot images. If an image is found,
control is passed to the image.
6.7.6

Boot Image Firmware Scan

The scan is performed by examining each 1 MB boundary for a defined set of flags that
identify the image as being POST, USER, or Alternate MOTLoad. POST is a user-
developed 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
MVME7100ET Single Board Computer Installation and Use (6806800K87G)
MOTLoad Firmware
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