Input/Output and CommunicationIntroductionReview of Direct Memory AccessDirect Memory AccessI/O Processors (Introduction)CPU Connection to I/O DevicesI/O ProcessorsCPU with I/O ProcessorTERMSThree Forms of CommandsThe Process of the IOPSerial CommunicationTwo types of Serial CommunicationSerial Communication BasicsIllustration of HandshakingAsynchronous Serial CommunicationSlide 17Line of transmissionSlide 19Synchronous TransmissionSynchronous Transmission FrameUniversal Asynchronous Receiver/Transmitters (UARTs)UARTsConclusionComputer Organization 147Input/Output and CommunicationChapter 10 Part IICS 147Andy LaiIntroductionI/O Processors–Input-Output ProcessorReview of DMABlock transfer commandsALU commandControl commandsSerial Communication–Explanation of the Basic–Asynchronous serial communication–Synchronous transmission–Introduction of Universal Asynchronous Receiver Transmitter (UARTs)Review of Direct Memory AccessDMA improves system performance by speeding up data transfer between memory and I/O SystemBypass CPU, allow CPU to be use in another process.DMA controllers must manipulates each data transfer from I/O devices, and can only read.Direct Memory AccessCPUI/ODevicesMemoryDirect Memory Access Controller(DMA)Address BusData BusControl BusI/O Processors (Introduction)I/O Processors also known as:I/O ControllersChannel ControllersPeripheral Processing units (PPU)Data ChannelCPU Connection to I/O DevicesI/O ProcessorsI/O Processors handles all of the interactions between the I/O devices and the CPU.I/O Processors communicates with input and output devices through separate address, data, and control lines. This provides an independent pathway for the transfer of information between external devices and internal memory.Relieves the CPU of ‘I/O device chores’Work LoadCPUCPU with I/O ProcessorTERMSInput-Output Processor (IOP)–Classified as a processor with direct memory access capability.–IOP fetches and execute its own instructionsIndependent of the CPUCPU initiating the IOP program–CPU is the master processor. IOP is considered the slave processors–There can be more than one or more IOP’sThree Forms of CommandsBlock transfer commands–Moves blocks data to IOP. Usually these instructions swap pages in and out of physical memory, and to load programs from disk memory.Arithmetic, logic, and Branch operations–IOP uses ALU instructions to manipulate the data so the process time for CPU is shorten.Control Command–Controls hardware. Ex: rewind the tape on a tape drive or ejecting a CD from a drive.The Process of the IOP•CPU Instructions•Sends Command to test IOP path•Status approved and sends I/O commands•CPU continues with other process•Request IOP status•Check status for correct transfer.•IOP Operations•Transfer status to Memory location•Access memory for IOP Commands•Conduct I/O transfer•I/O transfer completed, send status to CPU•Transfer status to memory locationSerial CommunicationTwo forms of communication–Parallel communicationTransfers more than one bit of data at a given timeN-bits transmitted at the same time through n- wiresFaster but requires many wires and is used in short distancesEX: Input/output devices, DMA controllers, and I/O processors–Serial CommunicationSerial communication refers to devices that cannot handle more than one bit of data at any given time by design.Requires one wire and is slower.Usually CPU use Parallel communication, if the device is serial, then the data is converted to use Parallel communicationEX: ModemsTwo types of Serial CommunicationAsynchronous Serial Communication–Interacts with devices outside of the computerEx: modem connecting to another computer–Transmit individual bytes instead of large blocks –Do not share a common clock.Synchronous Serial transmission–Transmits block of data in frames.Frames are had head in front of the data and a tail at the end of the data.–The head and tail contain information that allows the two computers to synchronize their clocksSerial Communication BasicsThere are parameters that must be agreed upon between the two computer system. One of them is the speed.–Also known as HandshakingDetermine speed and transfer protocol–Speed is measured by the number of bits per second (bps)–Also Know as Baud RateDevice must agree on number of data bits per data transmission.–Parity BitsError checking–Stop BitsEnd of transmissionIllustration of HandshakingI am 14,400 bpsOkI am 28,800 bpsI will speak 14,000 for youDataAsynchronous Serial CommunicationEach byte is transmitted separate entity.–The Device must be able to recognize:When transmission is occurring When to read a bit of dataWhen the transmission endsWhen the transmission is idle (no data being transmitted)Asynchronous Serial CommunicationDevice 1 transmission will output a ‘start bit’–A line of transmission is used to describe the communication.Device 2 receives and confirms the bit.Device 2 begins to read a data bit off the lineThen the process repeats however many data bits are on the line.The least significant bit is sent first and most important significant bit is sent last.Then Device 2 receives and confirms ‘stop bit’Line of transmissionIdleStartbitData 1 BitStopBitStartbitStop BitData 2 BitAsynchronous Serial CommunicationTransmitting numeric data is straight forwardTransmitting Characters are encoded with a binary value. –Most well know is American Standard Code for Information Interchange (ASCII)–Another is UNICODE.Synchronous TransmissionInstead of transmitting a start and stop bit for each data value, Synchronous transmission strings together several data values into a data block called a ‘frame.’There are several layers in the frame, similar to a data packet.There is a leading information, address of where the data is going, control ensure correct destination, the data it self, Cyclic redundancy check (CRC) to check there is no error and the trailing informationSynchronous Transmission FrameDataControlLeadingFlagTrailingFlagCRCAddress8 8 816n 8High Level Data Link Control(HDLC)Universal Asynchronous Receiver/Transmitters (UARTs)Asynchronous serial communication is a popular function. Manufacturers have designed special chip to deal with Asynchronous serial communication. This
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