| 摘要 |
An input/output sub-system for a digital data processing system having a microprogrammed processor and main memory in which the processor functions as a multiplexor for transferring data between a plurality of peripheral devices and the memory. The I/O controls for the peripheral devices share a common bus to the processor. The controls are slaved to the processor and operate to send or receive information over the common bus only in response to commands from the processor. However, any I/O control unit can signal the processor that it needs service. Each command addressed to one of the I/O control units is followed by status information returned on the bus to the processor by the I/O control. In addition, the status of an I/O control can be tested on special command from the processor. Each I/O control is buffered for storage of a block of data. A reference address pointing to the location of the Input/Output Descriptor in memory being executed by the processor is transferred to the control and stored in the buffer. It is returned to the processor after a Service Request by the control is acknowledged by the processor.
|
