mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 101

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

MOTOROLA
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:
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.
The MAC unit is tightly coupled to the OEP and features a three-stage execution pipeline.
To minimize silicon costs, the ColdFire MAC is optimized for 16 x 16 multiply
instructions. The OEP can issue a 16 x 16 multiply with a 32-bit accumulation and fetch a
32-bit operand in the same cycle. A 32 x 32 multiply with a 32-bit accumulation takes three
cycles before the next instruction can be issued. Figure 3-1 shows the basic functionality of
the ColdFire MAC. A full set of instructions is provided for signed and unsigned integers
plus signed, fixed-point, fractional input operands.
• Signed and unsigned integer multiplies
• Multiply-accumulate operations supporting signed, unsigned, and signed fractional
• Miscellaneous register operations
operands
Chapter 3. Hardware Multiply/Accumulate (MAC) Unit
3-1