Abstract: DMA adapters which perform programmed data transfer operations in response to descriptors are programmed by information in the same descriptors (and adapter logic responsive to that information) to perform various ancillary control functions relative to addressable I/O devices that conventionally would be addressed and controlled directly by a host (higher level) system processor (e.g., the processor that prepares the descriptors). The ancillary control functions are variable programmably in number (e.g., in the disclosed embodiment, one descriptor can define 0, 1 or 2 discrete ancillary control operations) and effects produced by each operation are programmably variable (e.g., ancillary operation can be used by the adapter to alter states of addressed devices; for example, to prepare a device that has been transferring data in one direction, in a half-duplex mode, for transferring data in the opposite direction, or to switch to a full duplex mode, etc.).

Abstract: A processor stores descriptors without explicit linkages, in non-contiguous memory locations, and sequentially hands them off to an adaptor which manages scheduling and processing of data transfers defined by the descriptors. Each descriptor is handed off in a request signalling process in which the processor polls the availability of a request register in the adaptor, and writes the address of a respective descriptor to that register when it is available. The adapter then schedules processing of the descriptor whose address is in the request register. The adapter manages a "Channel Descriptor Table" (CDT), which defines the order of processing of descriptors designated by the requests. In effect, the CDT defines a linked list queue into which the adapter installs descriptors, in the sequence of receipt of respective requests. Using the CDT information, the adapter retrieves successively queued descriptors and controls performance of operations (data transfer or other) defined by them.

Abstract: A known switch is mounted on a base of a switch actuator assembly. When the switch is to be actuated, an input shaft and switch actuator member are rotated together relative to the base. A helical return spring urges the input shaft back toward the initial position. When the input shaft and switch actuator member have been rotated together to an actuated position, the switch is actuated and the switch actuator member engages a stop surface. During continued rotation of the input shaft from the actuated position to an overtravel position, a pin connected with the input shaft moves away from one end of a slot in the switch actuator member. A helical overtravel spring is deflected along with the return spring. Deflection of the overtravel spring urges the switch actuator member and input shaft back toward their initial position relative to each other.

Abstract: A pressure transducer (50) of the type utilizing a diaphragm (8) with strain sensitive elements (14) formed in the diaphragm surface where the strain sensitive elements (14) are connected to an electronics assembly (4) to produce an electrical output in response to deflection of the diaphragm (8). A diaphragm assembly (26) is bonded to an intermediate support member (28) which is in turn bonded to a main support member (32) which is joined to a support collar (42) and hermetically sealed thereto with a sealing glass (40) where each element (2, 28, 32, 42) has a substantially matched coefficient of thermal expansion so as to reduce any induced thermal stresses and resultant measurement errors where the sealing glass (40) and the support collar (42) have a greater coefficient to produce a compressive type seal at high temperature.