
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
3-1
Chapter 3
Hardware Multiply/Accumulate (MAC) Unit
This chapter describes the MCF5272 multiply/accumulate (MAC) unit, which executes integer multiply,
multiply-accumulate, and miscellaneous register instructions. The MAC is integrated into the operand
execution pipeline (OEP).
3.1
Overview
The MAC unit provides hardware support for a limited set of digital signal processing (DSP) operations
used in embedded code, while supporting the integer multiply instructions in the ColdFire microprocessor
family.
The MAC unit provides signal processing capabilities for the MCF5272 in a variety of applications
including digital audio and servo control. Integrated as an execution unit in the processor’s OEP, the MAC
unit implements a three-stage arithmetic pipeline optimized for 16 x 16 multiplies. Both 16- and 32-bit
input operands are supported by this design in addition to a full set of extensions for signed and unsigned
integers plus signed, fixed-point fractional input operands.
The MAC unit provides functionality in three related areas:
•
Signed and unsigned integer multiplies
•
Multiply-accumulate operations supporting signed, unsigned, and signed fractional operands
•
Miscellaneous register operations
Each of the three areas of support is addressed in detail in the succeeding sections. Logic that supports this
functionality is contained in a MAC module, as shown in
Figure 3-1. ColdFire MAC Multiplication and Accumulation
X
+/-
Operand Y
Operand X
Shift 0,1,-1
Accumulator