Nortel Networks Circuit Card ユーザーズマニュアル

 NTBK51 Downloadable D-channel Handler daughterboard

A sanity timer is incorporated on the DDCH to prevent the MPU from getting 
tied-up as the result of a hardware or software fault. If the MPU encounters a 
hardware or software fault and enters a continuous loop, the sanity timer 
enables the DDCH to reset itself.

The bus timer presents an error signal to the MPU if an attempt to access a 
device did not receive acknowledgment within the bus time-out period of 
120 ms.

Downloading is performed in either of two modes: background mode or 
maintenance mode. Before a download takes place, a D-channel link must be 
configured. The following situations lead to software downloading:

•

during initialization when new software is installed

•

when enabling the card or application

•

during card reset (due to loss of software or corruption)

•

during a background audit

When new base or application software is installed on a CS 1000S, 
CS 1000M Cabinet, and Meridian 1 PBX 11C Cabinet, the download 
decision is made during system initialization. The actual MSDL base 
software download is done in background mode and can take several minutes 
to complete, depending on switch traffic and the size of the MSDL base 
software.

If a normal download enable command is executed, the MSDL base code and 
application is conditionally downloaded to the DDCH card. This conditional