Information

Reset, Clocking, and Initialization
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 4-19
4.3.3.2.3 EEPROM Data Format in Reset Configuration Mode
The I
2
C module expects that a particular data format be used for data in the EEPROM. A preamble should
be the first 3 bytes programmed into the EEPROM. It should have a value of 0xAA_55AA. The I
2
C
module checks to ensure that this preamble is correctly detected before proceeding further. Following the
preamble, there should be the two reset configuration words, programmed according to a particular format,
as shown in Figure 4-5.
The first 3 bytes hold the attributes and address offset. The addresses of the two reset configuration words
must be programmed to the offset of the reset configuration word low register (RCWLR) and reset
configuration word high register (RCWHR) respectively (see Section 4.5.1.1, “Reset Configuration Word
Low Register (RCWLR),” and Section 4.5.1.2, “Reset Configuration Word High Register (RCWHR)”).
The attributes should be programmed as follows: alternate configuration space (ACS) should be cleared
(0b0), byte enables should be all ones, and continue (CONT) should be set.
After the first 3 bytes, 4 bytes of data should hold the desired value of the reset configuration word. The
boot sequencer assumes that a big-endian address is stored in the EEPROM.
IMMRBAR value is prepended to the EEPROM address to generate the complete memory-mapped
register’s address.
When the I
2
C operates in reset configuration mode, the cyclic redundancy check (CRC) is ignored, as well
as any registers following the first two reset configuration words.
Figure 4-5. EEPROM Data Format for Reset Configuration Words Preload Command
Figure 4-6 shows an example of the CRC and EEPROM contents, including the preamble, reset
configuration words and additional initialization data. In this example, it is assumed that the EEPROM
01 4567
ACS
(0)
BYTE_EN
(1111)
CONT
(1)
RCWLR
ADDR[12–13]
RCWLR ADDR[14:21]
RCWLR ADDR[22:29]
Reset configuration word low [0–7]
Reset configuration word low [8–15]
Reset configuration word low [16–23]
Reset configuration word low [24–31]
ACS
(0)
BYTE_EN
(1111)
CONT
(1)
RCWHR
ADDR[12–13]
RCWHR ADDR[14–21]
RCWHR ADDR[22–29]
Reset configuration word high [0–7]
Reset configuration word high [8–15]
Reset configuration word high [16–23]
Reset configuration word high [24–31]