Functional Description - Nortel Circuit Card Installation Manual

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Functional description

Micro Processing Unit (MPU)
553-3001-211 Standard 3.00
NTBK22 MISP card
Refer to ISDN Basic Rate Interface: Installation and Configuration
(553-3001-218) and ISDN Basic Rate Interface: Features (553-3001-380) for
additional information.
Each MISP can support 4 line cards (UILC or SILC or any combination of the
two). Each line card supports 8 DSLs, therefore each MISP supports 32
DSLs. Since each DSL uses two B-channels and one D-channel the MISP
supports 64 B-channels and 32 D-channels. If the MISP is carrying packet
data, it must dedicate one of its D-channels to communicate with the external
packet handler. In this case the MISP supports only 31 DSLs.
The main functions of the MISP are:
• communicate with the Call Server CPU to report ISDN BRI status and
receive downloaded application software and configuration parameters
• manage Layer 2 and Layer 3 signaling that controls call connection and
terminal identification
• control terminal initialization and addressing
• assign B-channels for switched voice and data transmission by
communicating with the BRI terminal over the D-channel and allocating
to it an idle B-channel with appropriate bearer capabilities
• separate D-channel data from signaling information and route the data to
the packet handler
• send call control messages to ISDN BRI terminals over the D-channel
The MPU coordinates and controls data transfer and addressing of the
peripheral devices and communicates with the CPU using a message channel
on the CPU bus. The tasks that the MPU performs depend on the interrupts it
receives. The interrupts are prioritized by the importance of the tasks they
control.
August 2005