PNX1502E Datasheet, PDF (210/819 Pages) NXP Semiconductors – Connected Media Processor

Philips Semiconductors
Volume 1 of 1
PNX15xx Series
Chapter 6: Boot Module
4. The Boot From an I²C EEPROM
If none of the built-in scripts is suitable e.g., due to a different type of NAND-Flash or
a different memory organization or anything not matching the internal boot scripts, an
external serial boot EEPROM is required. Depending on the application
characteristics, this can be a small (1 Kilobyte or less) EEPROM that contains a small
boot script and starts the PNX15xx Series system in host-assisted mode or boot from
Flash memory or ROM devices. Alternately, a large serial EEPROM can be used to
contain a complete disk file system or an upload capability from another device than
Flash/ROM.
For a 2-Kilobyte or smaller EEPROM, the script must start at byte address 1 (not 0).
For a 4-Kilobyte or larger EEPROM, the boot script must start at byte address 0. More
details in Section 4.3. Each set of four successive bytes is assembled into a 32-bit
word value (the byte read first ends up as the least significant byte, LBS). The 32-bit
words are then interpreted as commands, as documented earlier in Section 2.3.
Remark: It has been seen that depending on the Write Protect pin status, some
EEPROMs do not behave the same way on a write of 0 bytes (Section 4.3). The
internal counter gets or does not get incremented which makes this rule of where the
first byte is located at address 0 or 1 different. Refer to EEPROM datasheet or try both
options.
4.1 External I²C Boot EEPROM Types
The PNX15xx Series Boot module supports all I²C EEPROMs (sometimes called 2-
wire EEPROMs) that use a 1-byte or 2-byte address protocol and respond to an I²C
device code 1010 (binary). Subtle differences exist between devices For example:
• It is recommended to avoid devices that have partial array write protection, since
such devices could be overwritten by accidental or intentional I²C writes, causing
boot failure during the next reset.
• Some devices may have additional functionality that is useful, like a watchdog
timer or a power voltage drop sensor.
• Availability from different vendors may vary.
• Programming protocols may vary.
Table 10 lists a variety of devices. This list is by no means exhaustive, nor has
operation for all these devices been verified.
Table 10: Examples of I²C EEPROM Devices
Size
Device
Write Protection
Coverage
Address Protocol Comment
256 bytes ATMEL 24C02
Full Array
1 byte
512 bytes ATMEL 24C04
Full Array
1 byte
1 kilobytes ATMEL 24C08
Full Array
1 byte
Tested
2 kilobytes PHILIPS PCF85116-3 Full Array
1 byte
2 kilobytes SUMMIT SMS8198 Full Array
1 byte
Includes power-on reset for board
system reset generation
12NC 9397 750 14321
Product data sheet
Rev. 2 — 1 December 2004
© Koninklijke Philips Electronics N.V. 2002-2003-2004. All rights reserved.
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