| 摘要 |
A microprocessor device is used in an adapter for a communications loop of the closed ring, one-way, token-passing local area network type. Each station has a host processor with a host CPU, a main memory, and a system bus, and has an adapter including the microprocessor tested according to the invention. The adapter coupled to the main memory by the system bus and includes a local CPU (the microprocessor), a local read/write memory, and a local bus. A transmit-and-receive controller is coupled to the local bus to directly access the local read/write memory; when this station receives a free token, the transmit-and-receive controller copies the message frame to be transmitted from the local read/write memory to the outgoing signal path, converting from parallel to serial. When a message addressed to this station is received, the controller converts it from serial to parallel, and copies the message frame into the local read/write memory via the local bus. Testing of the microprocessor is accomplished by internal self-test of the registers of the device, using the microcode of the control ROM initiated by a test control input.
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