Nortel Networks 553-3001-211 manual NTRB21 DTI/PRI/DCH Tmdi card Page 821

NTRB21 DTI/PRI/DCH TMDI card Page 821 of 894

Microprocessor

The NTRB21 is equipped with bit-slice microprocessors that handle the following major tasks:

•Task handler: also referred to as an executive. The task handler provides orderly per-channel task execution to maintain real-time task ordering constraints.

•Transmit voice: inserts digital pads, manipulates transmit AB bits for DS1, and provides graceful entry into T-Link data mode when the data module connected to the DTI/PRI trunk is answering the call.

•Receive voice: inserts digital pads and provides graceful entry into T-Link data mode when the data module connected to the DTI/PRI trunk is originating the call.

•T-Link data: a set of transmit and receive vectored subroutines which provides T-Link protocol conversion to and from the DM-DM protocol.

•Receive ABCD filtering: filters and debounces the receive ABCD bits and provides change of state information to the system.

•Diagnostics

•Self-test

Digital pad

The digital pad is an EPROM whose address-input to data-output transfer function meets the characteristics of a digital attenuator. The digital pad accommodates both µ255-Law and A-Law coding. There are 32 combinations each for µ255 to µ255, µ255 to A-Law, A-Law to µ255, and A-Law to A-Law. These values are selected to meet the EIA loss and level plan.

Circuit Card Description and Installation