Nortel Networks 553-3001-211 manual Download operation, Bus timer, System initialization

NTBK51 Downloadable D-channel Handler daughterboard Page 777 of 894

Sanity timer

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.

Bus timer

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.

Download operation

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

System initialization

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.

Card enabling or application enabling

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

Circuit Card Description and Installation