Nortel Circuit Card, Installation Manual, Page: 770 / 908

Page 770 of 906 NTBK22 MISP card
553-3001-211 Standard 3.00 August 2005
Refer to ISDN Basic Rate Interface: Installation and Configuration
(553-3001-218) and ISDN Basic Rate Interface: Features (553-3001-380) for
additional information.
Functional description
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
Micro Processing Unit (MPU)
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.