The Intel UPI-452 (Universal Peripheral Interface) is a 68 pin CHMOS Slave I O Processor with a sophisticated bi-directional FIFO buffer interface on the slave bus and a two channel DMA processor on-chip The UPI-452 is the newest member of Intel's UPI family of products It is a general-purpose slave I O Processor that allows the designer to grow a customized interface solution The UPI-452 contains a complete 80C51 with twice the on-chip data and program memory The sophisticated slave FIFO module acts as a buffer between the UPI-452 internal CPU and the external host CPU To both the external host and the internal CPU the FIFO module looks like a bi-directional bottomless buffer that can both read and write data The FIFO manages the transfer of data independent of the UPI-452 core CPU and generates an interrupt or DMA request to either CPU host or internal as a FIFO service request The FIFO consists of two channels the Input FIFO and the Output FIFO The division of the FIFO module array 128 bytes between Input channel and Output channel is programmable by the user Each FIFO byte has an additional logical ninth bit to distinguish between a data byte and a Data Stream Command byte Additionally Immediate Commands allow direct interrupt driven bi-directional communication between the UPI-452 internal CPU and external host CPU bypassing the FIFO The on-chip DMA processor allows high speed data transfers from one writeable memory space to another As many as 64K bytes can be transferred in a single DMA operation Three distinct memory spaces may be used in DMA operations Internal Data Memory External Data Memory and the Special Function Registers (including the FIFO IN FIFO OUT and Serial Channel Special Functions Registers)