EB632 datasheet(12/112 Pages) FREESCALE

12 / 112 page

Functional Differences Between MSC8101 (Mask 2K42A) and MSC8103 (Mask 2K87M), Rev. 2

Freescale Semiconductor

Boot

Note:

The bootloader supports access to serial EPROMs up to 512 KB with an address specification that is

accessed by 2 bytes.

The bootloader allocates a buffer for the first code block according to the address and size given in the opening 4

words and creates a BD that describes it. After the BD is ready, the bootloader starts reading the code block from

the EPROM. If checksum is enabled, the bootload calculates a checksum on the block word and compares the

calculated checksum to the loaded checksum. If the checksum is correct, the bootloader continues to the next

block. If the checksum fails, the bootloader tries to read the block again. After a second unsuccessful try, the

bootloader aborts.

To skip the checksum comparison, clear the checksum enable bit. If checksum is disabled, the bootloader program

continues loading the next code block after finishing the current one. When all code blocks are loaded, boot

execution starts from the start address given in the end block.

The bootloader program polls the BDs to check when a code block has been received. It does not use interrupts.

The load procedure is described in Figure 3.

Figure 3. Serial Boot Load Procedure

Load from serial EPROM

Configure I2C register and

parameter RAM

Disable software watchdog

Get 4 first words

first 32 bytes = 0?

ok?

Read Block

checksum

Enabled?

enabled?

Go to End

yes

Read Block and Calculate

Checksum

checksum

OK?

enabled?

First Error?

ok?

yes

ERROR- Stop boot

yes

Prepare next block address

Go to End

Read End block

Start boot execution

Calculate table address

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