The D igital Digital Logic Level Chapter 3 1

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1 The Digital Logic Level Chapter 3 1

2 Gates and Boolean Algebra (1) (a) A transistor inverter. (b) A NAND gate. (c) A NOR gate. 2

3 Gates and Boolean Algebra (2) The symbols and functional behavior for the five basic gates. (d) X= A.B (e) X= A + B 3

4 Boolean Algebra (a) Truth table for majority function of three variables (A,B,C). O/P is 0 if the majority of its I/P are 0. 1 if the majority of its I/P 1 (b) A circuit for (a). 4

5 Circuit Equivalence (1) C t ti f ( ) O (b) d () O t Construction of (a) NOT, (b) AND, and (c) OR gates using only NAND gates or only NOR gates. 5

6 Circuit Equivalence (2) Two equivalent functions (a) AB + AC, (b) A(B + C). 6

7 Circuit Equivalence (3) Some identities of Boolean algebra. 7

8 Circuit Equivalence (4) Alternative symbols for some gates: (a) NAND, (b) NOR, (c) AND, (d) OR 8

9 Circuit Equivalence (5) (a) The truth table for the XOR function (a) The truth table for the XOR function. (b-d) Three circuits for computing it. 9

10 Circuit Equivalence (6) (a) Electrical characteristics of a device. (b) Positive logic. (c) Negative logic. 10

11 Integrated Circuits An SSI chip containing four gates. SSI : Small scale integrated (1 to 10 gates) MSI : medium scale integrated (10 to 100 gates) LSI : large scale integrated (100 to 100,000 gates) VLSI: very large scale integrated >100,000 gates) 11

12 Combinational Circuits Multiplexers (1) An eight-input o/p depends d on i/p n control i/p, i/p is 2 n, 1o/p Multiplexer circuit. Used to select one of the i/p Used as parallel-to-serial cct Application: keyboard 12

13 Multiplexers (2) (a) An MSI multiplexer. (b) The same multiplexer l wired to compute the majority function. 13

14 Decoders n bits i/p, used to set one of the o/p 2 n to 1. Small memory consist of 8 chips A 3-to-8 decoder circuit. 14

15 Comparators A simple 4-bit comparator. o/p is 1 if A=B o/p is 0 otherwise 15

16 Programmable Logic Arrays A 12-input input, 6-output programmable logic array. The little squares represent fuses that can be burned out. 16

17 Arithmetic Circuit Shifters A 1-bit left/right shifter. 8 i/p, 8 o/p, control line C determine the direction of the shift 0 for left, 1 for right 17

18 Adders (1) (a) (b) (a) A truth table for 1-bit addition. (b) A circuit for a half adder. 18

19 Adders (2) (a) Truth table for a full adder. (b) Circuit for a full adder ( has carry i/p &o/p). 19

20 Arithmetic Logic Units ALU (1) A 1-bit ALU. Perform AND, OR, sum of two machine word. The cct perform AB, A+B, notb based on F 0, F 1 (00,01,10,11) ) 20

21 Arithmetic Logic Units (2) Eight 1-bit ALU slices connected to make an 8-bit ALU. The enables and invert signals are not shown for simplicity. 21

22 Clocks (a) A clock. (b) The timing diagram for the clock. (c) Generation of an asymmetric clock. 22

23 Memory (1 bit ) Latches (1) (a) NOR latch in state 0. (b) NOR latch in state 1. (c) Truth table for NOR. 23

24 Latches (2) A clocked SR latch. 24

25 Latches (3) A clocked D latch.

26 Flip-Flops (1) (a) A pulse generator. (b) Timing at four points in the circuit.

27 Flip-Flops (2) FF: the state transition does not occur when the clock is 1 but during the clock transition from 0 to 1 or 1 to 0. FF is edge triggered, whereas a latch is level trigger ADfli flip-flop.

28 Flip-Flops (3) D latches and flip-flops. a & b latch, c& d FF

29 Flip-Flops (4) Dual D flip-flop.

30 Flip-Flops (5) Octal flip-flop. flop.

31 Memory Organization (1) Logic diagram for four -bit (4 x 3) memory. Each row is one of the our 3-bit words. 8 i/p and 3 o/p. (I 0,I 1,I 2 ) are data, (A 0,A 1 ) re address, three for ontrol, CS for chip elect, RD for readrite, OE for o/p enable. hree o/p data To select this chip, CS, D,,(A 0 0,,A 1 1)

32 Memory Organization (2) (a) A noninverting buffer. (b) Effect of (a) when control is high. (c) Effect of (a) when control is low. (d) An inverting buffer.

33 Memory Chips (1) Two ways of organizing a 4-Mbit memory chip. (a) 19 address lines needed to address 2 19 bytes, 8 data in, out (b) Asserting rather than high or low. Opposite is negated (c) WE write enable, fig b 1 i/p & o/p arranged as 2048 X 2048 matrix (d) RAS (Row address strobe), CAS (Column address

34 Memory Chips (2) Two ways of organizing i a 512 Mbit memory chip.

35 Nonvolatile& volatile Memory Chips A comparison of various memory types. RAM: Random Access Memory, read and write, static and dynamic, static consists of FF, used for level 2 cache memory, very fast. Dynamic consists of cell each has transistor and tiny capacitor, need refresh( reloaded), small size, slow DDR (Double Data Rate) Synchronous DRAM, produce data on the rising and falling edge (Synchronous : waits for a clock signal before responding to control inputs ) ROM (Read only memory) EEPROM is byte erasable, Flash is a block erasable and rewritable

36 CPU Chips The logical pinout of a generic CPU. The arrows indicate input signals and output signals. The short diagonal lines indicate that multiple pins are used. For a specific CPU, a number will be given to tell how many. Pins divided into three types : address, data, and control

37 CPU Chips The control pins are grouped into: Bus control, interrupts, Bus arbitration, Coprocessor, Status, Miscellaneous. Bus control : Telling whether the CPU wants to read or write. interrupts : I/O assert a signal to the CPU and having it service the I/O device. Bus arbitration ti : Regulate traffic on the bus Coprocessor : Floating point chips Miscellaneous : Reset

38 Computer Buses (1) A computer system with multiple l buses.(external or

39 Computer Buses (2) Examples of bus masters and slaves. Master: is the active one Slave : is the passive one

40 Bus Width Growth of an Address bus over time. New: Multiplexed bus

41 Bus Clocking (1) Read timing on a synchronous bus.

42 Bus Clocking (2) Specification of some critical times.

43 Asynchronous Buses Operation of an asynchronous bus.

44 Bus Arbitration (1) What happens if two or more devices want to become bus master at the same time. I/O, CPU wants to read memory Many CPUs have a bus arbiter built into the CPU chip, but sometimes a separate chip is needed. When the device physically closet to the arbiter sees the grant, it checks to see if it made a request. If so, it takes over the bus but does not propagate the grant further down the line. If it has not made a request, it propagate the grant to the next device in the line. (daisy chaining) Bus arbiter may have more than one level (2, 4,8,16). Each device is attached to certain level and take priority. CPU is given the lowest priority. Modern computer systems put the memory on a separate bus from the Modern computer systems put the memory on a separate bus from the I/O devices so that they do not have to compete for accessing the bus.

45 Bus Arbitration (1) (a) A centralized one-level bus arbiter using daisy chaining. (b) The same arbiter, but with two levels.

46 Bus Arbitration (2) Decentralized bus arbitration.

47 Bus Operations (1) A block transfer. A block read of 4 words and takes 6 cycles

48 Bus Operations (2) Use of the 8259A interrupt controller. When the CPU commands an I/O, it usually expect an interrupt when the work is done Multiple devices, assign priority to each one and use arbiter to give priority to the most critical CPU handles the INT, gives INTA (ACK) issues the number of the device on the data bus, the CPU hardware uses this number to index into a table of pointers ( interrupt vectors ) to find the address of the procedure to run to service the interrupt.

49 Examples CPU: Pentium 4 The Pentium 4 physical pin out.

50 Pentium 4 Human hairs range from 20 microns to 100 microns in diameter. P4 has 55 million of transistors running at speeds up to 3.2 GHz Line width is.09 micron. It has deeper pipeline and two ALU. Some models of P4 have two level cache and some have 3 levels. All models have an 8-KB on chip SRAM (L1), the second level cache holds up to 256 KB of memory in the older models and up to 1 MB in the newer ones. P4 extreme edition has 2-MB level cache 3. Two primary external buses, synchronous. The memory bus is used to access the main SDRM, the PCI bus is used to talk to I/O devices. P4 consumes between 63watts and 82 watts.

51 The Pentium 4 s Logical Pinout Logical pinout of the Pentium 4. Names in upper case are the official Intel names for individual signals. Names in mixed case are groups of related signals or signal descriptions. P4 is 64- bit machine

52 P4 # symbol indicates that the signal is asserted low BR0 is used to request the bus. BR1 allows the device to make a high priority request. LOCK allows CPU to lock the bus. Address is 36 bits, 64 GB ADS signal is asserted to tell the target (memory) that the address lines is valid REQ indicate the type of the bus cycle (read on word or write a block) Five error lines are used to report floating-point errors, internal errors, machine check. Response group contains signals used by the slave to report back to the master RS contains the status code. TRDY indicates that the slave is ready to accept data from the master. BNR is used to assert a wait state when the target addressed cannot respond on time. D is used to put 8 data bytes onto the bus. DRDY is asserted to announce their presence. DBSY is used to tell the world that the bus is currently busy. RESET is used to rest the CPU

53 Pipelining on the Pentium 4 s Memory Bus Pipelining requests on the Pentium 4 s memory bus.

54 The UltraSPARC III (1) The UltraSPARC III CPU chip. It was introduced in 2000 at 600 MHz using.18 microns, 29 millions of tr. In 2002 the lines width dropped to.13 and the clock was raised to 1.2GHs Required 50 watts

55 The UltraSPARC III (2) The main features of the core of an UltraSPARC III

56 The 8051 (1) Physical pinout of the 8051.

57 The 8051 (2) Logical pinout of the It has 16 address lines, it can address up to 64 KB of memory, data bus is 8 bits. 32 I/O lines, each can be attached to button, switch. It has 4 KB of internal ROM A contains the 16 address line, D are 8 used for data transport, multeplexed A address RD and WR for external memory if needed. ALE (address latch enable) used when external memory present, PSEN (program store enable) 8051 wants to read from program memory, EA (external access) if high use the internal memory, TXD and RXD allow serial I/O, RST external device to reset the chip

58 Examples 1.The ISA Bus The PC/AT bus has two components, the original PC part and the new part. ISA ( Industry Standard Architecture)

59 2.The PCI Bus PCI bus (Peripheral Component Interconnect bus). The original PCI bus transferred 32 bits per cycle and ran at 33 MHz (30 nsec cycle time) for a total bandwidth of 133 MB/sec. The PCI bus runs at up to 66 MHz and can handle 64-bit transfers, for a total bandwidth of 528 MB/sec. AGP bus ( Accelerated Graphics Port bus ). The PCI bus is synchronous, like all PC buses going back to the original IBM PC All transactions on the PCI bus are between a master, officially called the initiator, and a slave, officially called the target The address and data lines are multiplexed. In this way, only 64 pins are needed on PCI cards for address plus data signals. On a read operation, during cycle 1, the master puts the address onto the bus. On cycle 2 the master removes the address and the bus is turned around so the slave can use it. On cycle 3, the slave outputs the data requested. On write operations, the bus does not have to be turned around because the master puts on both the address and the data.

60 2.The PCI Bus (1) Architecture of an early Pentium system. The thicker buses have more bandwidth than the thinner ones but the figure is not to scale.

61 The PCI Bus (2) The bus structure of a modern Pentium 4.

62 PCI Bus Arbitration The PCI bus uses a centralized bus arbiter. PCI bus arbitration ti uses a centralized bus arbiter. The bus arbiter is built into one of the bridge chips. Every PCI device has two dedicated lines running from it to the arbiter. One line, REQ#, is used to request the bus. The other line, GNT#, is used to receive bus grants. To request the bus, a PCI device (including the CPU), asserts REQ# and

63 The Master (initiator) and Slave (target) columns tell who asserts ( ) ( g ) the signal on a normal transaction. PCI bus transaction begins at the falling edge of CLK PCI Bus Signals(1) Mandatory PCI bus signals.

64 PCI Bus Signals(2) Optional PCI bus signals.

65 PCI Bus Transactions Examples of 32-bit PCI bus transactions. The first three cycles are used for read operation, then an idle cycle, and then three cycles for a write operation.

66 PCI Express At typical lpcie Express system.

67 PCI Express Protocol Stack (a) The PCI Express protocol stack. (b) The format of a packet.

68 The Universal Serial Bus (USB) A USB system consists of a root hub that plugs into the main bus, This hub has sockets for cables that can connect to I/O devices. The topology of a USB system is a tree with its root at the root hub, inside the computer. The cable consists of four wires: two for data, one for power (+5 volts), and one for ground. There is no traffic between two I/O devices. Every 1.00 ± 0.05 msec, the root hub broadcasts a new frame to keep all the devices synchronized in time.

69 The Universal Serial Bus (USB) The USB root hub sends out frames every 1.00 ms. SOF (Start of Frame) packet

70 The Universal Serial Bus (USB) USB supports four kinds of frames: control, isochronous, bulk, and interrupt. Control frames are used to configure devices, give them commands, and inquire about their status. Isochronous frames are for real-time devices such as telephones. Bulk frames are for large transfers to or from devices with no real-time requirements such as printers. interrupt frames are needed because USB does not support interrupts.

71 The Universal Serial Bus (USB) A frame consists of one or more packets, possibly some in each direction. Four kinds of packets exist: token, data, handshake, and special. Token packets are from the root to a device and are for system control. SOF, IN, and OUT packets are token packets, SOF (Start of Frame) packet is the first one in each frame and marks the beginning of the frame. IN token packet is a poll, asking the device to return certain data, Fields in the IN packet tell which bit pipe is being polled so the device knows which data to return, OUT token packet announces that data for the device will follow. DATA (used to transmit up to 64 bytes of information either way). handshake packets are defined: ACK (the previous data packet was correctly received), NAK (a CRC error was detected), and STALL (please wait I am busy right now). USB1 speed is 1.5 Mbps, USB 2 speed is 480 Mbps FireWire speed 400 Mbps, 800 Mbps

72 I/P CHIPS Chips UART (universal Asynchronous Receiver Transmitter). PIO (Parallel Input/ output) PIO Chips An 8255A PIO chip.

73 Address Decoding (1) Location of the EPROM, RAM, and PIO in our 64 KB

74 Address Decoding (2) Full address decoding. EPROM: 00000XXXXXXXXXXX RAM : 10000XXXXXXXXXXX PIO : XX

75 Address Decoding (3) Partial address decoding. EPROM: 1XX.. RAM : 10XXX PIO : 11XXXX..

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This page intentionally left blank 216 THE DIGITAL LOGIC LEVEL CHAP. 3 and in 1995, 2.1 came out. 2.2 has features for mobile computers (mostly for saving battery power). The bus runs at up to 66 MHz and