ADMC331BST datasheet(8/36 Pages) AD

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ADMC331

–8–

REV. B

BUS

EXCHANGE

DATA

ADDRESS

GENERATOR

DATA

ADDRESS

GENERATOR

R BUS

COMPANDING

CIRCUITRY

DMA BUS

PMA BUS

DMD BUS

PMD BUS

PROGRAM

SEQUENCER

INSTRUCTION

INPUT REGS

OUTPUT REGS

SHIFTER

INPUT REGS

OUTPUT REGS

MAC

INPUT REGS

OUTPUT REGS

ALU

SERIAL

PORT 0

RECEIVE REG

TRANSMIT REG

CONTROL

LOGIC

DM RAM

PM ROM

PM RAM

SERIAL

PORT 1

RECEIVE REG

TRANSMIT REG

TIMER

Figure 3. DSP Core Block Diagram

DSP CORE ARCHITECTURE OVERVIEW

Figure 3 is an overall block diagram of the DSP core of the

ADMC331, which is based on the fixed-point ADSP-2171. The

flexible architecture and comprehensive instruction set of the

ADSP-2171 allows the processor to perform multiple operations

in parallel. In one processor cycle (38.5 ns with a 13 MHz

CLKIN) the DSP core can:

• Generate the next program address.

• Fetch the next instruction.

• Perform one or two data moves.

• Update one or two data address pointers.

• Perform a computational operation.

This all takes place while the processor continues to:

• Receive and transmit through the serial ports.

• Decrement the interval timer.

• Generate three-phase PWM waveforms for a power inverter.

• Generate two signals using the 8-bit auxiliary PWM timers.

• Acquire four analog signals.

• Decrement the watchdog timer.

The processor contains three independent computational units:

the arithmetic and logic unit (ALU), the multiplier/accumulator

(MAC) and the shifter. The computational units process 16-bit

data directly and have provisions to support multiprecision com-

putations. The ALU performs a standard set of arithmetic and

logic operations; division primitives are also supported. The

MAC performs single-cycle multiply, multiply/add, multiply/

subtract operations with 40 bits of accumulation. The shifter

performs logical and arithmetic shifts, normalization, denormalization

and derive exponent operations. The shifter can be used to effi-

ciently implement numeric format control including floating-

point representations.

The internal result (R) bus directly 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 computa-

tional units. The sequencer supports conditional jumps and

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

counters and loop stacks, the ADMC331 executes looped code

with zero overhead; no explicit jump instructions are required

to maintain the loop.

Two data address generators (DAGs) provide addresses for

simultaneous dual operand fetches from data memory and

program memory. Each DAG maintains and updates four ad-

dress pointers (I registers). Whenever the pointer is used to

access data (indirect addressing), it is post-modified by the

value in one of four modify (M registers). A length value may

be associated with each pointer (L registers) to implement auto-

matic modulo addressing for circular buffers. The circular buff-

ering feature is also used by the serial ports for automatic data

transfers to and from on-chip memory. DAG1 generates only

data memory address but provides an optional bit-reversal

capability. DAG2 may generate either program or data memory

addresses, but has no bit-reversal capability.

Efficient data transfer is achieved with the use of five internal

buses:

• Program Memory Address (PMA) Bus

• Program Memory Data (PMD) Bus

• Data Memory Address (DMA) Bus

• Data Memory Data (DMD) Bus

• Result (R) Bus

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