lect18-datapath

# lect18-datapath - Lecture 18 Datapath Functional Units 18...

This preview shows pages 1–10. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Lecture 18: Datapath Functional Units 18: Datapath Functional Units 2 CMOS VLSI Design CMOS VLSI Design 4th Ed. Outline Comparators Shifters Multi-input Adders Multipliers 18: Datapath Functional Units 3 CMOS VLSI Design CMOS VLSI Design 4th Ed. Comparators 0’s detector: A = 00…000 1’s detector: A = 11…111 Equality comparator: A = B Magnitude comparator: A < B 18: Datapath Functional Units 4 CMOS VLSI Design CMOS VLSI Design 4th Ed. 1’s & 0’s Detectors 1’s detector: N-input AND gate 0’s detector: NOTs + 1’s detector (N-input NOR) A A 1 A 2 A 3 A 4 A 5 A 6 A 7 allones A A 1 A 2 A 3 allzeros allones A 1 A 2 A 3 A 4 A 5 A 6 A 7 A 18: Datapath Functional Units 5 CMOS VLSI Design CMOS VLSI Design 4th Ed. Equality Comparator Check if each bit is equal (XNOR, aka equality gate) 1’s detect on bitwise equality A[0] B[0] A = B A[1] B[1] A[2] B[2] A[3] B[3] 18: Datapath Functional Units 6 CMOS VLSI Design CMOS VLSI Design 4th Ed. Magnitude Comparator Compute B – A and look at sign B – A = B + ~A + 1 For unsigned numbers, carry out is sign bit A B A 1 B 1 A 2 B 2 A 3 B 3 A = B Z C A B ≤ N A B ≥ 18: Datapath Functional Units 7 CMOS VLSI Design CMOS VLSI Design 4th Ed. Signed vs. Unsigned For signed numbers, comparison is harder – C: carry out – Z: zero (all bits of A – B are 0) – N: negative (MSB of result) – V: overflow (inputs had different signs, output sign ≠ B) – S: N xor V (sign of result) 18: Datapath Functional Units 8 CMOS VLSI Design CMOS VLSI Design 4th Ed. Shifters Logical Shift: – Shifts number left or right and fills with 0’s • 1011 LSR 1 = 0101 1011 LSL1 = 0110 Arithmetic Shift: – Shifts number left or right. Rt shift sign extends • 1011 ASR1 = 1101 1011 ASL1 = 0110 Rotate: – Shifts number left or right and fills with lost bits • 1011 ROR1 = 1101 1011 ROL1 = 0111 18: Datapath Functional Units 9 CMOS VLSI Design CMOS VLSI Design 4th Ed....
View Full Document

## This note was uploaded on 01/15/2012 for the course ECE260A 660090 taught by Professor Bendak,michaelbeshara during the Fall '09 term at UCSD.

### Page1 / 31

lect18-datapath - Lecture 18 Datapath Functional Units 18...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online