Page 140 of 236 NTAK09 1.5 Mb DTI/PRI card553-3023-211 Standard 1.00 June 2001MicroprocessorThe NTAK09 is equipped with bit-slice microprocessors that handle thefollowing major tasks:• Task handler: also referred to as an executive, the task handler providesorderly per-channel task execution to maintain real-time task orderingconstraints.• Transmit voice: inserts digital pads, manipulates transmit AB bits forDS1, and provides graceful entry into T-Link data mode when the datamodule 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 isoriginating the call.• T-Link data: a set of transmit and receive vectored subroutines whichprovides T-Link protocol conversion to/from the DM-DM protocol.• Receive ABCD filtering: filters and debounces the receive ABCD bitsand provides change of state information to the system.• Diagnostics• Self-testDigital padThe digital pad is an EPROM whose address-input to data-output transferfunction meets the characteristics of a digital attenuator. The digital padaccommodates both μ255-law and A-Law coding. There are 32 combinationseach 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.Table 31Digital pad values and offset allocations (Part 1 of 2)Offset PAD set 0 PAD set 10 0dB –7db1 2dB –8db2 3dB –9db
