User`s manual

4.4 Flash ROM (System ROM)

The ﬂash ROM, sometimes called the system ROM, is a 1MB, nonvolatile,

writable ROM. After the SROM code initializes the AlphaPC64 system, ﬂash

ROM code prepares the system for booting. The ﬂash ROM headers, structure,

and access methods are described here.

4.4.1 Special Flash ROM Headers

The MAKEROM tool is used to place a special header on ROM image ﬁles. The

SROM allows the ﬂash ROM to contain several different ROM images, each

with its own header. The header informs the SROM where to load the image,

and whether or not it has been compressed with the MAKEROM tool. The

header is optional for ﬂash ROM containing a single image. If the header does

not exist, the 1MB ﬂash ROM is loaded and executed at physical address zero.

Figure 4–5 shows the header content.

Figure 4–5 Special Header Content

LJ04171A.AI5

Validation Pattern 5A5AC3C3

Inverse Validation Pattern A5A53C3C

Header Rev<7:0>Reserved<31:16>

Image Checksum

Image Size (Memory Footprint)

Decompression Flag

Destination Address Lower Longword

Destination Address Upper Longword

Header Size (Bytes)

Optional Firmware ID<63:32>

Header Checksum (excluding this field)

Firmware ID<15:8>

Optional Firmware ID<31:0>

Flash ROM Image Size

31 00

Table 4–2 describes each entry in the special header.

Functional Elements 4–9