Logical Dotting of Tri-State Drivers
Original Publication Date: 1988-Feb-01
Included in the Prior Art Database: 2005-Feb-14
The method described allows tri-state drivers to be dot-ORed onto a net when the location of the active driver is not known in advance. This allows for a simplified logical interconnect in those situations, such as the error line from a group of logical functions, i.e., memory cards, which may have randomly occurring errors. Another situation would be the interrupt line from a number of input devices. When the functions are implemented in bipolar circuits the usual solution is seen in Fig. 1. Open collector drivers are connected to the output line and are normally in the up level. The terminating resistor RT holds the line in a logical "1" state. Any driver may take command of the connection and pull it to the "0" state. When the driver returns (Image Omitted) to the "1" state, RT pulls the connection back to the "1" state.