mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 271

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Chapter 12
Enhanced Multiply-Accumulate Unit (EMAC)
12.1 Introduction
This chapter describes the functionality, microarchitecture, and performance of the
enhanced multiply-accumulate (EMAC) unit in the ColdFire family of processors.
12.1.1 Overview
The EMAC design provides a set of DSP operations that can improve the performance of
embedded code while supporting the integer multiply instructions of the baseline
ColdFire architecture.
The EMAC provides functionality in three related areas:
The ColdFire family supports two MAC implementations with different performance
levels and capabilities. The original MAC features a three-stage execution pipeline
optimized for 16-bit operands, with a 16×16 multiply array and a single 32-bit
accumulator. The EMAC features a three-stage pipeline optimized for 32-bit operands,
with a fully pipelined 32×32 multiply array and four 48-bit accumulators.
The first ColdFire MAC supported signed and unsigned integer operands and was
optimized for 16x16 operations, such as those found in applications including servo
control and image compression. As ColdFire-based systems proliferated, the desire for
more precision on input operands increased. The result was an improved ColdFire MAC
with user-programmable control to optionally enable use of fractional input operands.
Freescale Semiconductor, Inc.
1. Signed and unsigned integer multiplication
2. Multiply-accumulate operations supporting signed and unsigned integer operands as
3. Miscellaneous register operations
well as signed, fixed-point, and fractional operands
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