
2-6
ColdFire CF4e Core User’s Manual
For More Information On This Product,
Go to: www.freescale.com
User Programming Model
2.2.6 EMAC Programming Model
The registers in the EMAC portion of the user programming model, described in
Section Chapter 5, “Enhanced Multiply-Accumulate Unit (EMAC),” include the following
registers:
The EMAC provides the following program-visible registers:
The EMAC programming model includes 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.
Figure 2-4. EMAC Register Set
2.2.7 Floating-Point Programming Model
Figure 2-5 shows the FPU programming model.
31
0
MACSR
ACC0
ACC1
ACC2
ACC3
ACCext01
ACCext23
MASK
MAC status register
MAC accumulator 0
MAC accumulator 1
MAC accumulator 2
MAC accumulator 3
Extensions for ACC0 and ACC1
Extensions for ACC2 and ACC3
MAC mask register
F
Freescale Semiconductor, Inc.
n
.