Nortel Networks Circuit Card User Manual

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 NTBK51 Downloadable D-channel Handler daughterboard
download depends on the result of the check made by the CPU on the MSDL 
base code and application software.
If a forced download enable command is executed in LD 96, the MSDL base 
code and application are forced down to the DDCH card, even if the base and 
application software is already resident on the DDCH card. In order to 
complete a forced download, the following conditions must be met:
the DDCH card must be enabled
the D-channel port must be disabled
Card reset
After a card reset, the MSDL base code and the D-channel application 
software are validated by the CPU. The software is stored in flash EPROM 
on the DDCH card and does not have to be downloaded. But if the software 
is missing due to new installation, corruption, or loadware version mismatch, 
the CPU automatically downloads the base/application into the DDCH card.
Background audit
If a background audit of the card and associated applications finds that a 
download is required, the card is queued in the PSDL tree. Downloading is 
performed in background mode based on the entries in the PSDL tree.