Abstract: An ISDN multiprotocol communications controller for controlling a communication link of thte S.sub.2 type (LS.sub.21 to LS.sub.24) between a computer (COMP) and a set of terminals (T.sub.1, T.sub.2, . . .) through an automatic telephone branch exchange (PABX) comprising a basic controller (UEI) controlling the higher communication layers of the OSI model and a peripheral device (UPRI) executing the control of communications between the computer (COMP) and the other terminals, as well as the multiplexing and demultiplexing of the data channels of the link. The controller includes, in series, a dynamic allocation device (DADI) allocating the time channels (VT.sub.i, VT.sub.j) corresponding to the data channels, executing the concentration of m time channels of the link in n physical channels (with m>n) of a dual-access memory (DAMI) of the FIFO type, in transmission and reception, and a signal processor (PCSI) connected to a programmable memory (MMI.sub.