Nortel Networks Circuit Card - Manual (Page 771)

NTBK22 MISP card Page 771 of 906
Circuit Card Description and Installation
High-Level Data Link Controller (HDLC)
The HDLC is a format converter that supports up to 32 serial channels that
communicate at speeds up to 64 kbps. The HDLC converts messages into the
following two message formats:
• a serially transmitted, zero-inserted, CRC protected message that has a
starting and an ending flag
• a data structure
CPU to MISP bus interface
Information exchange between the CPU and the MISP is performed with
packetized messages transmitted over the CPU bus. This interface has a
16-bit data bus, an 18-bit address bus, and interrupt and read/write control
lines.
This interface uses shared Static Random Access Memory (SRAM) as a
communication exchange center between the CPU and the MPU. Both the
CPU and the MPU can access this memory over the transmit and receive
channels on the bus.
MISP network bus interface
The network bus interface:
• converts bit interleaved serial data received from the network bus into
byte interleaved data for transmission over the 32 time slots used by the
HDLC controller
• accepts byte interleaved data transmitted from the HDLC controller and
converts it into a bit interleaved data stream for transmission over the
network bus
Power consumption
Power consumption is +5V at 2 A; +15V at 50 mA; and -15V at 50 mA.