Processor Register Description

2.2.2 EMAC Programming Model

The registers in the EMAC portion of the user programming model, are described in Section Chapter 5, “Enhanced Multiply-Accumulate Unit (EMAC),” and include the following registers:

Four 48-bit accumulator registers partitioned as follows:

Four 32-bit accumulators (ACC0–ACC3)

Eight 8-bit accumulator extension bytes (two per accumulator). These are grouped into two 32-bit values for load and store operations (ACCEXT01 and ACCEXT23).

Accumulators and extension bytes can be loaded, copied, and stored, and results from EMAC arithmetic operations generally affect the entire 48-bit destination.

Eight 8-bit accumulator extensions (two per accumulator), packaged as two 32-bit values for load and store operations (ACCext01 and ACCext23)

One 16-bit mask register (MASK)

One 32-bit status register (MACSR) including four indicator bits signaling product or accumulation overflow (one for each accumulator: PAV0–PAV3)

These registers are shown in Figure 2-4.

 

31

0

 

 

 

 

 

MACSR

MAC status register

 

 

 

 

 

 

ACC0

MAC accumulator 0

 

 

 

 

 

 

ACC1

MAC accumulator 1

 

 

 

 

 

 

ACC2

MAC accumulator 2

 

 

 

 

 

 

ACC3

MAC accumulator 3

 

 

 

 

 

 

ACCext01

Extensions for ACC0 and ACC1

 

 

 

 

 

 

ACCext23

Extensions for ACC2 and ACC3

 

 

 

 

 

 

MASK

MAC mask register

 

 

 

 

 

 

 

 

Figure 2-4. EMAC Register Set

2.2.3Supervisor Programming Model

Only system control software is intended to use the supervisor programming model to implement restricted operating system functions, I/O control, and memory management. All accesses that affect the control features of ColdFire processors are in the supervisor programming model, which consists of registers available in user mode as well as the following control registers:

16-bit status register (SR)

32-bit supervisor stack pointer (SSP)

32-bit vector base register (VBR)

32-bit cache control register (CACR)

MOTOROLA

Chapter 2. ColdFire Core

2-5

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Motorola MCF5281, MCF5282 user manual Emac Programming Model, Supervisor Programming Model