| 摘要 |
PROBLEM TO BE SOLVED: To carry out the interface conversion and to perform the communication with no dependence on the SO constitution of a computer by using UART emulator, an AT command emulator and a communication protocol control means. SOLUTION: One of both ends of an ISDN communication universal board 1 is connected to an ISDN circuit 3, via a DSU(digital service unit) 2 with the other end connected directly to the bus of a computer respectively. The board 1 includes a universal matching interface circuitα, consisting mainly of an I interface control IC 4, a CPU 5 and a UART control circuit 6. The control routine contained in a ROM 8 plays a primary role in the execution of functions of a UART emulator, an AT command emulator, a V.110 protocol emulator and a PPP synchronous/asynchronous converter. As a result of this, the interface conversion is carried out, and the SO of the computer recognizes the circuit 3 as merely a COM port.
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