Chapter 2 Computational Units; Overview; Binary String; Unsigned - Analog Devices adsp-2100 Manual

Computational Units
2.1

OVERVIEW

This chapter describes the architecture and function of the three
computational units: the arithmetic/logic unit, the multiplier/
accumulator and the barrel shifter.
Every device in the ADSP-2100 family is a 16-bit, fixed-point machine.
Most operations assume a twos-complement number representation,
while others assume unsigned numbers or simple binary strings. Special
features support multiword arithmetic and block floating-point. Details
concerning the various number formats supported by the ADSP-2100
family are given in Appendix C.
In ADSP-2100 family arithmetic, signed numbers are always in twos-
complement format. The processors do not use signed-magnitude, ones-
complement, BCD or excess-n formats.
2.1.1

Binary String

This is the simplest binary notation; sixteen bits are treated as a bit pattern.
Examples of computation using this format are the logical operations:
NOT, AND, OR, XOR. These ALU operations treat their operands as
binary strings with no provision for sign bit or binary point placement.
2.1.2

Unsigned

Unsigned binary numbers may be thought of as positive, having nearly
twice the magnitude of a signed number of the same length. The least
significant words of multiple precision numbers are treated as unsigned
numbers.
2.1.3

Signed Numbers: Twos-Complement

In discussions of ADSP-2100 family arithmetic, "signed" refers to twos-
complement. Most ADSP-2100 family operations presume or support
twos-complement arithmetic. The ADSP-2100 family does not use signed-
magnitude, ones-complement, BCD or excess-n formats.
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