Method and apparatus to reduce register overhead in a serial digital interface

Abstract

A method and apparatus for transferring data between telephony communications lines having different frame transmission rates. A downlink data frame according to a first protocol (e.g. a ROLMlink frame) is transmitted, at a first data rate, from a private branch exchange (PBX) to a telephone's network interface. One or more fields of data from this frame are collected in shift register which is internal to the interface. After collection, the data is injected into a downlink data frame of the telephone's internal protocol (e.g. a GCI frame), which is being transmitted on the telephone side of the interface at a second data rate (different from the first data rate). Simultaneously with the injecting, one or more fields of data from an uplink data frame of the telephone's internal protocol are shifted into the same register for later injection into an uplink data frame, of the external protocol, destined for the PBX. This later injection occurs simultaneously with data from another downlink data frame, from the PBX side of the interface, being collected in the register.

Dependencies are inferred from the claim text.