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Enhanced Multiply-Accumulate Unit (EMAC)
Freescale Semiconductor
5-10
show relative alignment of input operands, the full 64-bit product, the resulting
40-bit product used for accumulation, and 48-bit accumulator formats.
Figure 5-7. Fractional Alignment
Figure 5-8. Signed and Unsigned Integer Alignment
Therefore, the 48-bit accumulator definition is a function of the EMAC operating mode. Given that each
48-bit accumulator is the concatenation of 16-bit accumulator extension register (ACCext
n
) contents and
32-bit ACC
n
contents, the specific definitions are:
if MACSR[6:5] == 00
/* signed integer mode */
Complete Accumulator[47:0] = {ACCext
n
[15:0], ACC
n
[31:0]}
if MACSR[6:5] == 01 or 11 /* signed fractional mode */
Complete Accumulator [47:0] = {ACCext
n
[15:8], ACC
n
[31:0], ACCext
n
[7:0]}
if MACSR[6:5] == 10
/* unsigned integer mode */
Complete Accumulator[47:0] = {ACCext
n
[15:0], ACC
n
[31:0]}
The four accumulators are represented as an array, ACC
n
, where
n
selects the register.
X
OperandY
OperandX
Product
Extended Product
Accumulator
8
Extension Byte Upper [7:0]
+
0
32
40
40
8
40
Extension Byte Lower [7:0]
32
23
8
Accumulator [31:0]
X
OperandY
OperandX
Product
Extended Product
Accumulator
32
32
32
32
32
8
8
8
24
8
8
+
Extension Byte Upper [7:0]
Extension Byte Lower [7:0]
Accumulator [31:0]
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...