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Peripherals Connecting

Peripherals Connecting. Fundamentals. Peripherals Connecting. Peripherals can be connected as: Memory Mapped Devices (MMIO) I/O bus (PMIO) Wired on PCB Externally wired I/O bus + Memory Mapped Via an Interface. Peripherals Connecting (cont). Memory Mapped Devices

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Peripherals Connecting

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  1. Peripherals Connecting Fundamentals

  2. Peripherals Connecting • Peripherals can be connected as: • Memory Mapped Devices (MMIO) • I/O bus (PMIO) • Wired on PCB • Externally wired • I/O bus + Memory Mapped • Via an Interface LM-18 Computer Science SSI Embedded Systems I

  3. Peripherals Connecting (cont) • Memory Mapped Devices • Peripheral object work as an ore or more memory address, readable, writeable or both. • Peripheral can have an interrupt line (not mandatory) • Programmers communicate with peripheral, writing or reading a particular memory address • WARNING in some HW r/w operation can generate a fault interrupt, when attempting to do an illegal operation, such read on address for writing and viceversa; when this occur a system crash must be handled. LM-18 Computer Science SSI Embedded Systems I

  4. Peripherals Connecting (cont) • I/O bus (PMIO) • Some HW architectures have a supplemental bus for I/O and instructions for reading & writing on this bus • I/O process doesn’t interfere with cpu-memory exchanging • Reading/Writing bus speeds can be different between memory and peripherals • I/O bus + Memory Mapped • Both method, tipical device is the Video Card on PC LM-18 Computer Science SSI Embedded Systems I

  5. Peripherals Connecting (cont) • On Board Interfaces • Bus Bridges • Adapt a bus to another • Speed adjustment • Electrical adjustment • Electrical Insulating • Limit interrupt rate to principal bus LM-18 Computer Science SSI Embedded Systems I

  6. Peripherals Connecting (cont) • On Board interfaces (cont) • Bus bridges (cont) • Local Bus • Eisa • LAN • SCSI • PCI • USB • Bus Bridged vs peripherals • P2P wire (SATA disks) • Multiplexed wire • IDE/EIDE • USB • …. • PCB wired (PCI cards) LM-18 Computer Science SSI Embedded Systems I

  7. Peripherals Connecting (cont) • On Board interfaces (cont) • Bus bridged (cont) • Generally are microprocessor controlled cards able to do complex I/O operation with simply interface commands • Ex: LAN Cards receive destination MAC address and data buffer, then perform complete I/O: • Carrier On • Test power on line • Collision:Detected: random wait and retryNot detected: transmit msg one bit at timeVerify Transmitted: OK->return NOK & #retry>0 -> retransmit … • …. LM-18 Computer Science SSI Embedded Systems I

  8. Peripherals Connecting (cont) • On Board interfaces (cont) • Directly Wired On PCB • Wired outside PCB • Most Common: • I2C • SPI • Ethernet • USB • RS232 LM-18 Computer Science SSI Embedded Systems I

  9. Peripherals Connecting (cont) • Point to Point (P2P) • One physical connection for device • Multiplexed Devices (MUX) • One physical connection for devices LM-18 Computer Science SSI Embedded Systems I

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