National Semiconductor PC16552C Manual
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TL/F/11195PC16552C Dual UART/DMA Micro Channel Adapter AN-770National SemiconductorApplication Note 770Greg DeJagerJuly 1991PC16552C Dual UART/DMAMicro Channel AdapterTable Of ContentsINTRODUCTION AND FEATURESPC16552C ADAPTER BLOCK DIAGRAMPC16552C ADAPTER USER’S GUIDEPOS–PROGRAMMABLE OPTION SELECTAn overview of the Micro Channel Programmable OptionSelect (POS), a unique feature which replaces all adapterjumpers and switches with programmable configuration reg-isters.A. POS MechanismB. Adapter Description File (ADF)C. Configuration UtilitiesD. POS RegistersE. PC16552C Adapter POS Register DesignMICRO CHANNEL BUS INTERFACEGeneral information on the adapter interface to the MicroChannel, applicable to any adapter design, and specific in-formation on the design of the PC16552C Adapter.A. Micro Channel Control SignalsB. Data BusC. Address DecodeD. UART InterfaceE. InterruptsMICRO CHANNEL BUS ARBITRATIONAn overview of the bus arbitration system implemented onall Micro Channel machines.A. Central ArbiterB. Local ArbiterPC16552C ADAPTER DMA INTERFACE DESIGNThe design of the PC16552C Adapter’s Local Arbiter andinterface to the UART DMA request signals is described indetail.A. Design ConsiderationsB. DMA Request EnableC. DMA Request PrioritizationD. Arbitration Vector SelectionE. Local ArbiterF. FairnessG. Terminal Count InterruptSOFTWAREA. Programming the Micro Channel DMA ControllerB. Driver ProgramsEISA BUS DESIGN COMPARISONBrief description of a possible EISA bus serial port/DMAdesign.APPENDICESA. ADF Listing (@6e6D.adf)B. PAL… EquationsAPPENDICES (Continued)C. SchematicsD. Layout DrawingE. Bill of MaterialsINTRODUCTIONThe PC16552C integrates two NS16550AF UARTs into asingle package. The product provides control for two inde-pendent PC-AT… and PS/2… compatible serial ports. In ad-dition, the on-board FIFOs and DMA request strobes of thePC16552C create the basis for a high-performance serialport design.Advancing modem technology is causing a substantial in-crease in serial transfer baud rates, putting a severe strainon existing serial port designs. Personal computer systemsare unable to keep up with transfer rates that are nowreaching 115k baud. The PC16552C allows the serial portdesigner to design ports that can handle these faster datarates. Transmitter and Receiver FIFOs buffer up to 16 bytesof data each, and request strobes signal the system DMAcontroller to transfer datato empty transmitter FIFOs andfrom full receiver FIFOs. DMA burst transfers can movedata from the serial I/O ports to system RAM very quicklywith no latency time and no attention from the system CPU.This document contains a user’s guide for the adapter anddiscusses the considerations involved in designing any Mi-cro Channel Adapter equipped with a DMA slave. It gives anoverview of the Micro Channel POS mechanism, adapterinterface and bus arbitration system. The design of thePC16552C Serial/DMA Adapter, intended as an example ofa DMA slave serial adapter, is described in detail. A descrip-ton of the software necessary to facilitate four simultaneousfile transfers serviced by the Micro Channel DMA controlleris also included.PC16552C ADAPTER FEATURES# Two independent PC-AT and PS/2 compatible serialports with FIFOs capable of running all existing NS16450and NS16550AF software.# All configuration done through POS mechanism. Nohardware jumpers or switches.# Serial ports relocatable to all eight standard I/O address-es.# Serial interrupts available on IRQ3 and IRQ4.# Hardware interface between UART FIFO DMA requestsand the Micro Channel bus arbitration and DMA system.# POS configurable priority levels for UART DMA requests.# Support for software enable/disable of UART DMA re-quests.# POS configurable Fairness feature for UART DMA re-quests.# Automatic interrupt generation and DMA request disableupon receipt of DMA Terminal Count.# Two DB-9 connectors for the two RS-232 compatible se-rial ports.C1995 National Semiconductor Corporation RRD-B30M75/Printed in U. S. A. |
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