Intel PCH-LP, Programming Manual

Page: 23 / 90

523462 23
Intel Confidential
Descriptor Overview
4 Descriptor Overview
The Flash Descriptor is a data structure that is programmed on the SPI flash part on
Broadwell PCH-LP based platforms. The Descriptor data structure describes the layout
of the flash as well as defining configuration parameters for the PCH. The descriptor is
on the SPI flash itself and is not in memory mapped space like PCH programming
registers. The maximum size of the Flash Descriptor is 4 KBytes. It requires its own
discrete erase block, so it may need greater than 4 KBytes of flash space depending on
the flash architecture that is on the target system.
The information stored in the Flash Descriptor can only be written during the
manufacturing process as its read/write permissions must be set to Read Only when
the computer leaves the manufacturing floor.
The Descriptor has 9 basic parts:
• The Flash signature at the bottom of the flash (offset 10h) must be 0FF0A55Ah in
order to be in Descriptor mode.
Figure 4-1. Flash Descriptor (Broadwell PCH-LP)