DesingAutomation Handsout 2 1

•  •  •  •  • 

2

DesingAutomation Handsout 2

DesingAutomation Handsout 2 3 DesingAutomation Handsout 2 4

DesingAutomation Handsout 2 5 DesingAutomation Handsout 2 6

DesingAutomation Handsout 2 7 DesingAutomation Handsout 2 8

DesingAutomation Handsout 2 9 DesingAutomation Handsout 2 10

11 DesingAutomation Handsout 2 12 DesingAutomation Handsout 2

13 DesingAutomation Handsout 2 14 DesingAutomation Handsout 2

15 DesingAutomation Handsout 2 16

Logic Level Design Automation

DesingAutomation Handsout 2

17

n  u Transistor-Level u Switch-Level u Gate-Level u Register-Transfer-Level u System-Level u Mixed-Level (Mixed-Mode)

DesingAutomation Handsout 2 18

.

n Transistor-level u  u  SPICE :

n  Switch-level u 

. u  ,

. u SPICE net-list

DesingAutomation Handsout 2

19

n Gate-level or logic-level

u  1 . u  . u Verilog, VHDL

n Register-transfer-level (RTL) u  . u 

u Verilog, VHDL

DesingAutomation Handsout 2 20

n  System-Level

t  t  t SystemC, System-Verilog, Spec-C

DesingAutomation Handsout 2

21

n  Mixed-level u  ,

n  Mixed-mode

u The simulator use different mechanism for different levels (e.g. a timing-driven numerical integration and event-driven technique)

n  Hardware-Software co-simulator u The solution for digital design problems contains

programmable hardware.

DesingAutomation Handsout 2 22

n  The simulator kernel u  .

n  u 

u  . u  .

DesingAutomation Handsout 2

23

n  u  u 

n  u  u  u  u 

DesingAutomation Handsout 2 24

Gate-level modeling and simulation n  Signal modeling n Gate modeling n Delay modeling n Connectivity modeling n  Simulation mechnism

u Event-driven u Compiler-driven u Demand-driven

DesingAutomation Handsout 2

25

Signal modeling

n  Binary or Boolean signals u  ‘0’ , ‘1’ u  ‘X’ : unknown u  ‘U’ : uninitialized u  strength of signal

t weak, strong, etc.

DesingAutomation Handsout 2 26

Gate modeling

n Truth table u  the table has a row for

each conbination of input signal value.

n  Subroutine u By machine instructions

A truth-table modeling of a two input NAND gate.

DesingAutomation Handsout 2

27

Delay modeling

n The propagation delay model u Fixed delay with the gate’s output u A delay depend on “the output’s fanout” u Zero-delay u Unit-delay

DesingAutomation Handsout 2 28

Delay modeling cont’d. n  The rise/fall delay model

u Different delay are used when when an output signals rise and when it falls

n  The inertial delay model u The property observed in physical circuits. u The input pulse should have minimal width in order

to have any effect at the output. n  The inertial delay model can be combined with both

the propagation and the rise/fall delay model.

DesingAutomation Handsout 2

29

A 2-input NAND gate and its switching input signals (a); the corresponding output signal in the propagation delay model (b), in the rise/fall delay model.

DesingAutomation Handsout 2 30

Connectivity modeling

n  Simulator should have suitable data structure to represent the connectivity of all gates in the network.

DesingAutomation Handsout 2

31

Compiler-driven simulation

n The best choice occurs in the context of synchronous circuits.

The core of synchronous circuit.

DesingAutomation Handsout 2 32

A simple circuits composed of logic gates

Code for the zero-delay simulation

DesingAutomation Handsout 2

33

The appearing of a “glitch” on net n9 in the circuit when using unit-delay model.

DesingAutomation Handsout 2 34

Pseudo-code meant for the compiler-driven simulation of the circuit using the unit-delay model DesingAutomation Handsout 2

35

Event-driven simulation

n Recompute signals that are actually changing. n A signal change is called an event. n Different delay models can be incorporated in

the simulator relatively easily. n  event-queue or event-list is the central data

structure.

DesingAutomation Handsout 2 36 The array implementation of the event-queue

DesingAutomation Handsout 2

37

The time-wheel implementation of the event-queue DesingAutomation Handsout 2 38

Pseudo-code of event-driven simulation function

DesingAutomation Handsout 2

39 DesingAutomation Handsout 2