Browse Prior Art Database

High-Speed Serial Communication Protocol

IP.com Disclosure Number: IPCOM000043320D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Canova, FJ: AUTHOR [+6]

Abstract

A method is described for communicating between computer equipment and input/output controllers at remote locations, particularly during trouble-shooting periods. The protocol presented provides an efficient and unique technique of synchronizing individual data exchanges. This is done on a controller-originated start bit at a transfer rate based on the controller's microprocessor instruction cycle time. The key to this protocol's efficiency is the way its microprocessor initiates a data transfer, using the same bidirectional line, and then synchronizes with the responding device in such a way that the entire data exchange requires only the originated start bit from the controller. In Fig. 1, a simplified timing diagram for the protocol is shown.

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High-Speed Serial Communication Protocol

A method is described for communicating between computer equipment and input/output controllers at remote locations, particularly during trouble-shooting periods. The protocol presented provides an efficient and unique technique of synchronizing individual data exchanges. This is done on a controller-originated start bit at a transfer rate based on the controller's microprocessor instruction cycle time. The key to this protocol's efficiency is the way its microprocessor initiates a data transfer, using the same bidirectional line, and then synchronizes with the responding device in such a way that the entire data exchange requires only the originated start bit from the controller. In Fig. 1, a simplified timing diagram for the protocol is shown. During the read sequence, the controller microprocessor prepares to transmit a -START bit, -COMMAND/+DATA bit and - READ/+WRITE bit by loading its internal I/O register. Executing an OUT I/O microinstruction to the bidirectional port address transmits the controlling bits to the connected device. The microprocessor then executes a microinstruction to position the next outbound bit. After sending the last of the three READ SEQUENCE bits, the microprocessor immediately begins sampling the data being sent back by the connected device. The microprocessor then monitors the data exchange through microcode. A polling sequence, as shown in Fig. 2, is used to sample the data bits in order to determine that no other devices are connected to the line at this time. The embodiment of this communication method is a serial console permanently attached to a controller using only one twisted pair of wires. A serial console is used to display register and memory contents while the transmission is taking place. Microcode subroutines are used for servicing the device and are a permanent part of the microprocessor's read- only storage (ROS). The console will recognize the poll sequence and synchronize with the controllers-originated start bit. After re...