Chapter 3. Hardware Multiply/Accumulate (MAC) Unit
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.
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.
Summary of Contents for DigitalDNA ColdFire MCF5272
Page 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Page 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Page 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Page 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Page 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Page 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Page 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Page 338: ...13 44 MCF5272 User s Manual Application Examples ...
Page 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Page 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Page 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Page 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...