MD82C237-12

82C237 March 1997 CMOS High Performance Programmable DMA Controller Description The 82C237 is a modified version of the 82C37A. The 82C237 is fully software and pin for pin compatible with the 82C37A but provides an additional mode for 16-bit DMA transfers, as well as enhanced speed. Each channel may be individually programmed for 8-bit or 16-bit data transfers. The 82C237 controller can improve system performance by allowing external devices to transfer data directly to or from system memory. Memory-to-memory transfer capability is also provided, along with a memory block initialization feature. DMA requests may be generated by either hardware or software, and each channel is independently programmable with a variety of features for flexible operation. The 82C237 is designed to be used with an external address latch, such as the 82C82, to demultiplex the most significant 8 bits of address. An additional latch is required to temporarily store the most significant 8 bits of data if 16-bit memory-to-memory transfers are desired. The 82C237 can be used with industry standard microprocessors such as 80C286, 80286, 80C86, 80C88, 8086, 8088, 8085, Z80, NSC800, 80186 and others. Multimode programmability allows the user to select from three basic types of DMA services, and reconfiguration under program control is possible even with the clock to the controller stopped. Each channel has a full 64K address and word count range, and may be programmed to autoinitialize these registers follow...