| 摘要 |
PURPOSE: A method for transferring a data using an L-bus in a telephone network access subsystem(TNAS) of a large capacity communication processing system is provided to improve a processing rate by transmitting a control data between boards through an L-bus, a parallel bus. CONSTITUTION: A trunk interface unit(310) is connected to a public switched telephone network(101) to receive 4E1, switches a time slot to connect 4 subhighway(SHW) to a processor interface unit(312) to perform a digital trunk interface(TLI) function and a link signal interface(LSI) function. The trunk interface unit(TNIA)(312) is connected to the processor interface unit(312) through an L-bus(301) so as to be interfaced with an interoffice trunk circuit of the public switched phone network (PSTN)(101) which uses a CEPT mode under the control of the processor interface unit(TPIA)(312), and transmits and receives signal information of a trunk line which uses a tone and an R2 signaling mode. The trunk interface unit(310) receives an R2 signal, provides a ring back tone, and includes a network synchronizing circuit for synchronizing a transfer bit of a trunk line. The trunk interface unit(310) uses a 2.048 MHz clock extracted from the trunk line as an input clock. A local clock generated from the network synchronizing circuit of the trunk interface unit(310) is 16.384 MHz. That is, the trunk interface unit(310) generates the 16.384 MHz in synchronization with the 2.048 MHz extracted from the trunk line, divides it to provide various clocks(4M,2M,8KHz clock) required by the processor interface unit(312) and a subscriber modem connecting unit(314).
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