摘要:
There is disclosed apparatus and a method for extending a parallel channel of the host processor over a serial link to a remote peripheral device. The apparatus includes a microprocessor within I/O channel extension logic which responds to either instructions or data from a host processor. The instructions are of the type commanding the I/O device to perform a specific operation and the data is provided in response to requests for data from the I/O device. The channel extension logic is coupled to the host processor's channel and thus is able to obtain data from the host storage by cycle steal techniques. Within the channel extension logic are means to serialize the information and transmit it in a serial manner over the link. The microprocessor within the channel extension logic creates a frame, including a control byte, which identifies the type of information followed by the data, which frame is then communicated over the serial link to the I/O device. The I/O device also includes a microprocessor and associated logic which responds to the frames communicated by the channel extension logic and generates a frame consisting of a control byte identifying the information type and associated data which is then communicated back over the serial link to the channel extension logic to request action by the channel extension logic or indicate completion of the operation. The I/O device may, for instance, request data be obtained from or stored in the host memory by cycle steal techniques and thereby utilize the features of the host and host channel despite only being coupled thereto by a serial link.
摘要:
A micro processor controlled user programmable communications multiplexer subsystem (herein referred to by the symbol PCS) capable of transmitting and receiving data on any one or more of 32 communications lines simultaneously. Each line may be dynamically assigned to a variety of communication characteristics, such as line speeds, character lengths, synchronous, or asynchronous operation, and code structures as well as protocol selections.The system of the invention provides the capability for the user to write his communications programs using novel operations commands that provide code structure and protocol independence as well as communication line independence. Various hardware features and queuing techniques are employed in order to maintain high transmission rates.Variable line scanning in the Teleprocessing Time Division Multiplexer of the PCS is programmably permissible; i.e., the time base for line scanning is fixed and is a multiple of the communication line rate, although the actual line to be scanned is programmably variable. The program ability is provided by a continuously scanned storage array which contains physical line addresses of the time division multiplexer. The scanning mechanism, while running, prioritizes the transmit buffer servicing of the individual lines.