34 PPC11A 6U VME Single Board Computer
Publication No. PPC11A-HRM/1
4.5.1 Boot Flash
The top 16 MB of Flash memory on the first Flash bank is used as Boot Flash, and
holds initialization and operating system boot routines. The Boot Flash region
contains two independent 8 MB boot areas (Main and Alternate). The active boot
image can be selected using P15 pins 1 to 4 during development (see
).
NOTE
The recovery area is on SPI Flash (see
4.5.2 User Flash
Any Flash that is not used as Boot Flash is designated as User Flash and is intended
to hold user application code or data. The processor’s integrated Flash Controller
uses CS1 to access User Flash. CS1 also provides access to the areas accessed by CS0
(at the top of the Flash array), but is not affected by the state of the
4.5.3 Paged Flash Mode
Due to limitations on the size of the processor memory map, a paged mode is
provided where the User Flash area is divided into 256 MB pages. This mode is
enabled and controlled by the
NOR Flash Page Register (offset 0x636)
4.5.4 Flash Sector Protection
The PPC11A uses Cypress S29GL Flash devices, which provide advanced methods
of sector protection to ensure the integrity of code data contained in the Flash array.
Protection is defined on a per-sector basis, where a sector is 128 KB in size. Locked
sectors cannot be erased or programmed, they may only be read.
No write protection of Flash is provided by hardware. Software must be used to
configure the Flash devices to protect against corruption of Flash data. The following
types of protection are provided:
•
Persistent sector protection provides non-volatile protection that remains in place
when a board is power cycled or reset. Each Flash sector may be set as locked
(write-protected) or unlocked (write-enabled) by writing to configuration
registers within the Flash. The configuration of this protection is only possible
when a jumper is fitted on the
Flash Protection Unlock link (P15 pins 7 and 8)
this condition is not met, the software is unable to change the sector protection
and those sectors that are locked may not be erased or reprogrammed under any
circumstances
•
Non-persistent protection may also be used. In this case, sectors locked using
Persistent mode may not be erased or reprogrammed, but previously unlocked
may now be locked. However, this protection is only present until a power cycle
or hardware reset occurs
CAUTION
Do not rely on non-persistent protection, as it may be subsequently altered by software. If further protection
is required, use the Persistent protection method.
Содержание PPC11A
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Страница 113: ...Publication No PPC11A HRM 1 Connectors 113 Figure 6 2 Rear Connector Position ...