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National Semiconductor INS8154N RAM, Input/Output (RAM I/O) 40-PIN DIP IC
The RAM Input/Output Chip is LSI device which provides random access memory and peripheral interfacing for microcomputer system. The RAM portion contains 1024 bits of static RAM organized as 128x8, The I/O portion consists of two peripheral ports of eight bits each. Each of the I/O pin in the two ports may be defined as an input or an output to provide maximum flexibility. Each port may be read from or written to in a parallel (8-byte) mode. To improve efficiency and simplify programming in control-based applications, a single bit of I/O in either port may be set, cleared or read with a single microprocessor instruction. In addition to basic I/O, one of the ports, port A, may be programmed to operate in several types of strobed mode with handshake. Strobed mode together with optional interrupt operation permit both high speed parallel data transfers and, interface to a wide variety of peripherals with no external logic.