Motorola MSC8101 ADS User's Guide Page 69

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Related Reading
Reset Configuration and Boot 2-17
checksum. The checksum is calculated by XORing the current word bit by bit with the
result of XORing previous words. The value of bit i of the current result is equal to
XORing bit i of the current word with bit i of the previous result. After the entire block is
loaded, the calculated checksum is compared to the loaded checksum to verify that the
code loading completed correctly. Note that the checksum is calculated on all the block
words, starting from the address.
A handshaking mechanism between the host and the slave indicates the status of the code
loading. The handshake mechanism uses one flag of the Interface Control Register (ICR)
and two flags in the Host Control Register (HCR). The host can set a flag in the ICR to
ignore the checksum comparison. If the flag is set, the checksum should be compared.
The SC140 core of the slave MSC8101 sets a flag in the HCR to indicate the completion
of code loading. It sets a different flag to indicate the occurrence of an error during the
checksum checks. The host MSC8101 ignores this flag if it does not need the checksum
checks.
2.5 Related Reading
C
MSC8101 User’s Guide (This manual)
Chapter 5, Balancing Between the
PowerPC System and Local Buses
Chapter 8, Host Interface (HDI16)
Appendix C, Bootloader Program
MSC8101 Reference Manual
Chapter 3, External Signals
Chapter 4, System Interface Unit
(SIU)
Chapter 5, Reset
Chapter 6, Boot
Chapter 12, PowerPC System Bus
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