Isolation of Multiple Communications Functions From Each Other
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Multi-line communications adapter 10 shares control of the same data communications line by the mutually incompatible X.21 switched connect/disconnect protocol and SDLC/BSC (Synchronous Data Link Control/ Binary Synchronous Communication) transfer protocols. The X.21 switched connect/disconnect function is isolated into a reentrant microcode module. Commands from tasks that require connection or disconnection of the data link are routed to the X.21 module. The X.21 module 11 has the ability to modify line supervisor module 12 to cause it to route character interrupt control to the X.21 module 11 instead of to the normal SDLC/BSC protocol modules 12 and 13. This is done by the X.21 module for the X.21 data link connect/disconnect phase shown symbolically by dashed lines 14.