Bidirectional Open Drain Latching Buffer Circuit
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
An open drain latching buffer circuit with built-in pull-up devices is used to both drive and receive from open drain nets utilizing a common I/O port. A known keyboard/controller interface for IBM personal computers (PCs) in a net consists of a keyboard clock line, a keyboard data line, a transmit data line, a keyboard inhibit line and a keyboard disconnect line. Off chip open drain buffers, a manual keyboard disconnect switch and five pull-up resistors complete the interface. Fig. 1 is a block diagram of a keyboard/controller interface which utilizes a bidirectional keyboard clock line (keyboard clock and keyboard inhibit), a keyboard data line (send/receive) and a keyboard disconnect line.