International Business Machines Corporation

Steven A Schmitt

Anthony Richard Bonaccio

David Otto Lewis

Brent Allen Carlson

James E Donaldson

Lloyd S Heim

Gregory G Floryance

Kenneth A Moe

Thomas H Miller

A controller device interfacing method and a low level device interface are provided for use between at least one controller and a plurality of devices in a direct access storage device. Message and command and data information are received and transmitted between the controller and the device. Responsive to a received predetermined read data command, read data function hardware transmits the requested data to the controller. Responsive to a received predetermined write data command, write data function hardware writes the received data from the controller to a device. Received message information is blocked from received data information so that message information is transmitted at any time within and between data information transmissions. The low level device interface supports two wire serial data transfer and provides improved data rate performance.

Low level device interface for direct access storage device including

A differential transceiver transmission line integrity detector detects both open and short circuits in the transmission lines. The two transmission lines are terminated at both ends by selected impedances. A driver coupled to each of the transmission lines drives the lines with data signals. Signal levels on the lines are detected and compared with expected levels to generate line integrity indications. Both open and short conditions are detected and indicated by the line integrity indications.

Differential transceiver with line integrity detection

A computer system executes instructions for an I/O device not attached to the system. A quasi I/O attachment device is responsive to the commands for the unattached I/O device and generates an interrupt condition. The interrupt condition causes the command instructions for the unattached I/O device to be translated to command instructions for an I/O device connected to the computer system. The I/O device attached to the system performs the designated operation and generates associated I/O device status data. This associated I/O device status data is translated into I/O device status data for the unattached I/O device and thus permits a program for operating an unattached I/O device to operate instead an I/O device attached to the system which otherwise could not be operated by that program. A second embodiment performs the emulation of the unattached I/O device remotely of the central processing unit in the computer system.

Computer system with post execution I/O emulation

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Rochester, MN, United States of America

Steven A Schmitt