Enhanced Multiply-Accumulate Unit (EMAC)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
4-17
then operandX[31:0] = {Rx[31:16], 0x0000}
else operandX[31:0] = {Rx[15:0],
0x0000}
}
else {operandY[31:0] = Ry[31:0]
operandX[31:0] = Rx[31:0]
}
/* perform the multiply */
product[63:0] = (operandY[31:0] * operandX[31:0]) << 1
/* check for product rounding */
if (MACSR.R/T == 1)
then { /* perform convergent rounding */
if (product[23:0] > 0x80_0000)
then product[63:24] = product[63:24] + 1
else if ((product[23:0] == 0x80_0000) && (product[24] == 1))
then product[63:24] = product[63:24] + 1
}
/* sign-extend to 48 bits and combine with accumulator */
/* check for the -1 * -1 overflow case */
if ((operandY[31:0] == 0x8000_0000) && (operandX[31:0] == 0x8000_0000))
then product[71:64] = 0x00
/* zero-fill */
else product[71:64] = {8{product[63]}}
/* sign-extend */
if (inst == MSAC)
then result[47:0] = ACCx[47:0] - product[71:24]
else result[47:0] = ACCx[47:0] + product[71:24]
/* check for accumulation overflow */
if (accumulationOverflow == 1)
then {MACSR.PAVn = 1
MACSR.V = 1
if (MACSR.OMC == 1)
then /* accumulation overflow,
saturationMode enabled */
if (result[47] == 1)
then result[47:0] = 0x007f_ffff_ff00
else result[47:0] = 0xff80_0000_0000
}
/* transfer the result to the accumulator */
ACCx[47:0] = result[47:0]
}
MACSR.V = MACSR.PAVn
MACSR.N = ACCx[47]
if (ACCx[47:0] == 0x0000_0000_0000)
then MACSR.Z = 1
else MACSR.Z = 0
if ((ACCx[47:39] == 0x00_0) || (ACCx[47:39] == 0xff_1))
then MACSR.EV = 0
else MACSR.EV = 1
break;
case 2:
/* unsigned integers */
if (MACSR.OMC == 0 || MACSR.PAVn == 0)
then {
MACSR.PAVn = 0
/* select the input operands */
if (sz == word)
then {if (U/Ly == 1)
then operandY[31:0] = {0x0000, Ry[31:16]}
else operandY[31:0] = {0x0000, Ry[15:0]}
if (U/Lx == 1)
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
