EE213 Digital Integrated Circuits II Lecture 01: From Architecture to Layout Prof. Pingqiang Zhou Chapter 4 Chapter Chapter 1 Chapter EE213 L01 From Architecture to Layout.1 Pingqiang, ShanghaiTech, 2017 Coping with Complexity How to design System-on-Chip or Microprocessor? Many millions (even billions!) of transistors Tens to hundreds of engineers The Core i7 die and major components. http://techreport.com/review/15818/intel-core-i7-processors Microcontroller-based system on a chip https://en.wikipedia.org/wiki/Atom_(system_on_chip) EE213 L01 From Architecture to Layout.2 Pingqiang, ShanghaiTech, 2017 Structured Design Hierarchy: Divide and Conquer Recursively system into modules Regularity Reuse modules wherever possible Ex: Standard cell library Modularity: well-formed interfaces Allows modules to be treated as black boxes Locality Physical and temporal EE213 L01 From Architecture to Layout.3 Pingqiang, ShanghaiTech, 2017 Design Abstraction Levels SYSTEM MODULE + GATE CIRCUIT Vin Vout DEVICE G S D n+ n+ EE213 L01 From Architecture to Layout.4 Pingqiang, ShanghaiTech, 2017 Design Abstractions Architecture: User’s perspective, what does it do? Instruction set, registers MIPS, x86, Alpha, PIC, ARM, … Microarchitecture Single cycle/multicycle, pipelined, superscalar? Ex: 80386, 80486, Pentium, Atom, AMD, Phenom, … Logic: how are functional blocks constructed Ripple carry, carry lookahead, carry select adders Circuit: how are transistors used Complementary CMOS, pass transistors, domino Physical: chip layout Objects: datapaths, memories, random logic EE213 L01 From Architecture to Layout.5 Pingqiang, ShanghaiTech, 2017 Gajski Y-Chart EE213 L01 From Architecture to Layout.6 Pingqiang, ShanghaiTech, 2017 MIPS Processor - An Example EE213 L01 From Architecture to Layout.7 Pingqiang, ShanghaiTech, 2017 1 - (MIPS) Architecture (Simple 32-bit RISC) Example: subset of MIPS processor architecture Drawn from Patterson & Hennessy, chapter 4 Consider 8-bit subset using 8-bit datapath Only implement 8 registers ($0 - $7) $0 hardwired to 00000000 8-bit program counter Interested in RISC? See http://baike.baidu.com/view/736344.htm EE213 L01 From Architecture to Layout.8 Pingqiang, ShanghaiTech, 2017 Instruction Set format example encoding 6 5 5 5 5 6 R add $rd, $ra, $rb 0 ra rb rd 0 funct 6 5 5 16 I beq $ra, $rb, imm op ra rb imm 6 26 J j dest op dest EE213 L01 From Architecture to Layout.9 Pingqiang, ShanghaiTech, 2017 Fibonacci (in C Language) f0 = 1; f-1 = -1 fn = fn-1 + fn-2 f = 1, 1, 2, 3, 5, 8, 13, … EE213 L01 From Architecture to Layout.10 Pingqiang, ShanghaiTech, 2017 Fibonacci (in Assembly Language) EE213 L01 From Architecture to Layout.11 Pingqiang, ShanghaiTech, 2017 Fibonacci (in Binary Code) 1st statement: addi $3, $0, 8. How do we translate this to machine language? format example encoding 6 5 5 5 5 6 R add $rd, $ra, $rb 0 ra rb rd 0 funct 6 5 5 16 I beq $ra, $rb, imm op ra rb imm 6 26 J j dest op dest EE213 L01 From Architecture to Layout.12 Pingqiang, ShanghaiTech, 2017 Fibonacci (in Binary Code) Machine language program EE213 L01 From Architecture to Layout.13 Pingqiang, ShanghaiTech, 2017 2 - (MIPS) Microarchitecture Multicycle marchitecture EE213 L01 From Architecture to Layout.14 Pingqiang, ShanghaiTech, 2017 Multicycle Controller EE213 L01 From Architecture to Layout.15 Pingqiang, ShanghaiTech, 2017 ALU Decoder Unit EE213 L01 From Architecture to Layout.16 Pingqiang, ShanghaiTech, 2017 3 - (MIPS) Logic Design Start at top level Hierarchically decompose MIPS into units Top-level interface 2-phase memread crystal ph1 memwrite clock oscillator generator ph2 MIPS 8 processor adr 8 external writedata reset memory 8 memdata EE213 L01 From Architecture to Layout.17 Pingqiang, ShanghaiTech, 2017 Top-Level MIPS Block Diagram EE213 L01 From Architecture to Layout.18 Pingqiang, ShanghaiTech, 2017 Hierarchical Design mips controller alucontrol datapath standard bitslice zipper cell library alu inv4x flop ramslice fulladder or2 and2 mux4 nor2 inv nand2 mux2 tri EE213 L01 From Architecture to Layout.19 Pingqiang, ShanghaiTech, 2017 HDLs Hardware Description Languages Widely used in logic design Verilog and VHDL Describe hardware using code Document logic functions Simulate logic before building Synthesize code into gates and layout - Requires a library of standard cells EE213 L01 From Architecture to Layout.20 Pingqiang, ShanghaiTech, 2017 Verilog Example – Full Adder mips controller alucontrol datapath standard bitslice8-Bit Adderzipper in ALU cell library alu inv4x flop ramslice fulladder or2 and2 mux4 nor2 inv nand2 mux2 tri EE213 L01 From Architecture to Layout.21 Pingqiang, ShanghaiTech, 2017 Verilog Example – Full Adder module fulladder(input a, b, c, output s, cout); sum s1(a, b, c, s); carry c1(a, b, c, cout); endmodule module carry(input a, b, c, output cout) assign cout = (a&b) | (a&c) | (b&c); endmodule EE213 L01 From Architecture to Layout.22 Pingqiang, ShanghaiTech, 2017 4 – (MIPS) Circuit Design Circuit design is concerned with arranging transistors to perform a particular logic function. How should logic be implemented? NANDs and NORs vs. ANDs and ORs? Fan-in and fan-out? How wide should transistors be? These choices affect speed, area, power Logic synthesis makes these choices for you Good enough for many applications Hand-crafted circuits are still better EE213 L01 From Architecture to Layout.23 Pingqiang, ShanghaiTech, 2017 Transistors as Switches Can view MOS transistors as electrically-controlled switches Source Gate Drain Source Gate Drain Polysilicon Polysilicon SiO2 SiO2 1 n+ n+ p+ p+ S D p bulk Si n bulk Si g = 0 g = 1 d d d OFF nMOS g ON s s s d d d OFF pMOS g ON s s s EE213 L01 From Architecture to Layout.24 Pingqiang, ShanghaiTech, 2017 CMOS Inverter A Y VDD 0 1 1 0 OFFON 01 A Y ONOFF A Y GND EE213 L01 From Architecture to Layout.25 Pingqiang, ShanghaiTech, 2017 CMOS NAND Gate A B Y 0 0 1 OFFON ONOFF 0 1 1 Y 01 1 0 1 A OFFON 1 1 0 10 B ONOFF EE213 L01 From Architecture to Layout.26 Pingqiang, ShanghaiTech, 2017 Complementary CMOS Complementary CMOS logic gates pMOS pull-up nMOS pull-down network network pMOS pull-up network inputs output a.k.a. static CMOS nMOS pull-down network Pull-up OFF Pull-up ON Pull-down OFF Z (float) 1 Pull-down ON 0 X (crowbar) EE213 L01 From Architecture to Layout.27 Pingqiang, ShanghaiTech, 2017 Series and Parallel a a a a a 0 0 1 1 nMOS: 1 = ON g1 g2 0 1 0 1 pMOS: 0 = ON b b b b b (a) OFF OFF OFF ON Series: both must be ON a a a a a 0 0 1 1 g1 g2 Parallel: either can be ON 0 1 0 1 b b b b b (b) ON OFF OFF OFF a a a a a g1 g2 0 0 0 1 1 0 1 1 b b b b b (c) OFF ON ON ON a a a a a g1 g2 0 0 0 1 1 0 1 1 b b b b b (d) ON ON ON OFF EE213 L01 From Architecture to Layout.28 Pingqiang, ShanghaiTech, 2017 Conduction Complement Complementary CMOS gates always produce 0 or 1 Ex: NAND gate Series nMOS: Y=0 when both inputs are 1 Thus Y=1 when either input is 0 Y Requires parallel pMOS A B Rule of Conduction Complements Pull-up network is complement of pull-down Parallel -> series, series -> parallel EE213 L01 From Architecture to Layout.29 Pingqiang, ShanghaiTech, 2017 CMOS NOR Gate A B Y 0 0 1 A 0 1 0 1 0 0 B 1 1 0 Y EE213 L01 From Architecture to Layout.30 Pingqiang, ShanghaiTech, 2017 Exercises - Compound Gates EE213 L01 From Architecture to Layout.31 Pingqiang, ShanghaiTech, 2017 Example: Carry Logic assign cout = (a&b) | (a&c) | (b&c); g1 a x a p1 b p2 b p4 b i4 c p3 i3 a p5 p6 g2 cn g4 cout a y cout c n3 i1 a n5 n6 c i2 g3 a n1 b n2 b n4 b z c Transistors? Gate Delays? EE213 L01 From Architecture to Layout.32 Pingqiang, ShanghaiTech, 2017 Gate-level Netlist module carry(input a, b, c, output cout) wireg1 x, y, z; a x b andg2 g1(x, g4a, b); a y and g2(y, a, coutc); c andg3 g3(z, b, c); b or zg4(cout, x, y, z); endmodulec This is a technology-independent structural description, because generic gates have been used and the actual gate implementations have not been specified. EE213 L01 From Architecture to Layout.33 Pingqiang, ShanghaiTech, 2017 Transistor-Level Netlist module carry(input a, b, c, output cout) wire i1, i2, i3, i4, cn; tranif1 n1(i1, 0, a); tranif1 n2(i1, 0, b); a p1 b p2 b p4 tranif1 n3(cn, i1, c); i4 c p3 i3 a p5 p6 tranif1 n4(i2, 0, b); cn tranif1 n5(cn, i2, a); cout c n3 i1 a n5 n6 tranif0 p1(i3, 1, a); i2 tranif0 p2(i3, 1, b); a n1 b n2 b n4 tranif0 p3(cn, i3, c); tranif0 p4(i4, 1, b); tranif0 p5(cn, i4, a); tranif1 n6(cout, 0, cn); tranif0 p6(cout, 1, cn); endmodule tranif1 corresponds to nMOS transistors that turn ON when the gate is 1 while tranif0 corresponds to pMOS transistors that turn ON when the gate is 0. EE213 L01 From Architecture to Layout.34 Pingqiang, ShanghaiTech, 2017 SPICE Netlist .SUBCKT CARRY A B C COUT VDD GND MN1 I1 A GND GND NMOS W=1U L=0.18U AD=0.3P AS=0.5P MN2 I1 B GND GND NMOS W=1U L=0.18U AD=0.3P AS=0.5P MN3 CN C I1 GND NMOS W=1U L=0.18U AD=0.5P AS=0.5P MN4 I2 B GND GND NMOS W=1U L=0.18U AD=0.15P AS=0.5P MN5 CN A I2 GND NMOS W=1U L=0.18U AD=0.5P AS=0.15P MP1 I3 A VDD VDD PMOS W=2U L=0.18U AD=0.6P AS=1 P MP2 I3 B VDD VDD PMOS W=2U L=0.18U AD=0.6P AS=1P MP3 CN C I3 VDD PMOS W=2U L=0.18U AD=1P AS=1P MP4 I4 B VDD VDD PMOS W=2U L=0.18U aAD=0.3Pp1 AS=1Pb p2 b p4 MP5 CN A I4 VDD PMOS W=2U L=0.18U AD=1P AS=0.3P i4 c p3 i3 a p5 p6 MN6 COUT CN GND GND NMOS W=2U L=0.18U AD=1P AS=1P cn MP6 COUT CN VDD VDD PMOS W=4U L=0.18U AD=2P AS=2P cout CI1 I1 GND 2FF c n3 i1 a n5 n6 CI3 I3 GND 3FF i2 CA A GND 4FF a n1 b n2 b n4 CB B GND 4FF CC C GND 2FF CCN CN GND 4FF CCOUT COUT GND 2FF .ENDS Transistors are specified by lines beginning with an M as follows: Capacitors are specified by lines beginning with C as follows: EE213 L01 From Architecture to Layout.35 Pingqiang, ShanghaiTech, 2017 5 – (MIPS) Physical Design Layout Schematic Routing Floorplan Placement “Electronic Design Automation: Synthesis, Verification, and Test (Systems on Silicon),” by Laung-Terng Wang, Yao-Wen Chang, and Kwang-Ting Cheng, Morgan Kaufmann Publishing, 2009.