The TP3401, TP3402 and TP3403 are complete monolithic transceivers for data transmission on twisted pair subscriber loops. They are built on National’s double poly microCMOS process, and require only a single a5 Volt supply. Alternate Mark Inversion (AMI) line coding, in which binary ‘1’s are alternately transmitted as a positive pulse then a
negative pulse, is used to ensure low error rates in the presence of noise with lower emi radiation than other codes such as Bi- phase (Manchester).
Full-duplex transmission at 144 kb/s is achieved on a single twisted wire pair using a burst-mode technique (Time Com- pression Multiplexed). Thus the device operates as an ISDN ‘U’ Interface for short loop applications, typically in a PBX environment, providing transmission for 2 B channels and 1 D channel. On #24 cable, the range is at least 1.8 km
System timing is based on a Master/Slave configuration, with the line card end being the Master which controls loop timing and synchronisation. All timing sequences necessary for loop activation and de-activation are generated on-chip.
Selection of Master and Slave mode operation is pro- grammed via the Microwire Control Interface.
A 2.048 MHz clock, which may be synchronized to the sys- tem clock, controls all transmission-related timing functions.
For the TP3401, this clock must be provided from an exter- nal source; the TP3402 includes an oscillator circuit requir- ing an external crystal. The TP3403 includes the functions of both the TP3401 and the TP3402.
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