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AD73460

Six-Input Channel Analog Front End

Analog Devices 

AD73460

ARCHITECTURE OVERVIEW

The AD73460 instruction set provides flexible data moves and

multifunction (one or two data moves with a computation) instruc-

tions. Every instruction can be executed in a single processor

cycle. The AD73460 assembly language uses an algebraic syntax

for ease of coding and readability. A comprehensive set of devel-

opment tools supports program development.

DATA

ADDRESS

GENERATORS

DAG 1 DAG 2

PROGRAM

SEQUENCER

POWER-DOWN

CONTROL

AD73460

MEMORY

16K PM 16K DM

(OPTIONAL (OPTIONAL

8K)

8K)

PROGRAMMABLE

I/O

AND

FLAGS

FULL MEMORY

MODE

PROGRAM MEMORY ADDRESS

DATA MEMORY ADDRESS

PROGRAM MEMORY DATA

EXTERNAL

ADDRESS

BUS

EXTERNAL

DATABUS

DATA MEMORY DATA

ARITHMETIC UNITS

ALU MAC SHIFTER

SERIAL PORTS

SPORT 0 SPORT 1

TIMER

BYTE DMA

CONTROLLER

ADSP-2100 BASE

ARCHITECTURE

REF

SERIAL PORT

SPORT 2

ADC1 ADC2 ADC3 ADC4 ADC5 ADC6

ANALOG FRONT END

SECTION

Figure 1. Functional Block Diagram

Figure 1 is an overall block diagram of the AD73460. The pro-

cessor section contains three independent computational units:

the ALU, the multiplier/accumulator (MAC), and the shifter. The

computational units process 16-bit data directly and have provi-

sions to support multiprecision computations. The ALU performs

a standard set of arithmetic and logic operations; division primi-

tives are also supported. The MAC performs single-cycle multiply,

multiply/add, and multiply/subtract operations with 40 bits of

accumulation. The shifter performs logical and arithmetic shifts,

normalization, denormalization, and derive exponent operations.

The internal result (R) bus connects the computational units so

that the output of any unit may be the input of any unit on the

next cycle.

A powerful program sequencer and two dedicated data address

generators ensure efficient delivery of operands to these compu-

tational units. The sequencer supports conditional jumps,

subroutine calls, and returns in a single cycle. With internal

loop counters and loop stacks, the AD73460 executes looped

code with zero overhead; no explicit jump instructions are

required to maintain loops.

Two data address generators (DAGs) provide addresses for

simultaneous dual operand fetches (from data memory and

program memory). Each DAG maintains and updates four

address pointers. Whenever the pointer is used to access data

(indirect addressing), it is post-modified by the value of one of

four possible modify registers. A length value may be associated

with each pointer to implement automatic modulo addressing

for circular buffers.

The two address buses (PMA and DMA) share a single external

address bus, allowing memory to be expanded off-chip, and the two

databuses (PMD and DMD) share a single external databus. Byte

memory space and I/O memory space also share the external buses.

An interface to low cost byte-wide memory is provided by the

Byte DMA port (BDMA port). The BDMA port is bidirectional

and can directly address up to four megabytes of external RAM

or ROM for off-chip storage of program overlays or data tables.

The AD73460 can respond to 11 interrupts. There can be up to

six external interrupts (one edge-sensitive, two level-sensitive, and

three configurable) and seven internal interrupts generated by

the timer, the serial ports (SPORTs), the Byte DMA port, and

the power-down circuitry. There is also a master RESET signal.

The two serial ports provide a complete synchronous serial

interface with optional companding in hardware and a wide

variety of framed or frameless data transmit and receive modes

of operation.

ANALOG FRONT END

The analog front end (AFE) of the AD73460 is configured as a

separate block that is normally connected to either SPORT0 or

SPORT1 of the DSP section. As it is not hardwired to either

SPORT, users have total flexibility in how they wish to allocate

system resources to support the AFE. It is also possible to

further expand the number of analog input channels connected

to the SPORT by cascading an AD73360 device external to

the AD73460.

The AFE is configured as six input channels. It comprises six

independent encoder channels, each featuring signal conditioning,

programmable gain amplifier, sigma-delta A/D converter, and

decimator sections. Each of these sections is described in further

detail later in this data sheet. All channels share a common

internal reference whose nominal value is 1.25 V. Figure 2 shows

a block diagram of the AFE section of the AD73460. It shows six

input channels along with a common reference. Communication

to all channels is handled by the SPORT2 block, which interfaces

to either SPORT0 or SPORT1 of the DSP section.

–10–

REV. A

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