Abstract: This circuit is a trunk type interface circuit which interfaces between duplicate copies of an ISDN system and T-carrier facilities. The circuit is controlled by a digital signal processor which has a 16-bit wide data bus. The digital signal processor is capable of supporting various Zero Byte Time Slot Interchange (ZBTSI) techniques. Also included is an administrative microprocessor which collects data concerning the operation of the trunk circuit and transmits this information to the ISDN system. The administrative microprocessor also receives information from currently unused data bits in the input bit stream from the ISDN system. The trunk circuit includes one receiver which collects and stores data transmitted by the ISDN system. Another receiver collects and stores data transmitted via the T-carrier facilities. The trunk circuit also includes two transmitters. One transmitter converts previously formatted data to T-carrier compatible data and transmits the data via the T-carrier facilities.

Abstract: This circuit converts data in an ISDN data format to data in a T-carrier compatible data format and vice versa. The converted data is then stored in a memory for subsequent transmission. Due to the format differences, the data may be discontinuous. This circuit stores the data in memory in a contiguous fashion to promote and to facilitate the subsequent transmission of the data. This circuit includes a timing and control arrangement which indicates the size of each channel and frame of input data. This circuit generates memory addresses for the storage of both ISDN and T-carrier formatted data which are contiguous over multiple frames of data. A counting arrangement of this circuit converts data received in a modulo 32 format to stored data in a modulo 24 format or vice versa. In addition, this circuit provides output signals for generating proper framing bits and extended superframing information.