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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Intel XScale
®
Processor
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
170
Order Number: 306262-004US
Two new instruction formats were added for coprocessor 0: Multiply with Internal
Accumulate Format and Internal Accumulate Access Format. The formats and
instructions are described next.
3.8.3.1.1
Multiply with Internal Accumulate Format
A new multiply format has been created to define operations on 40-bit accumulators.
Table 9, “MRC/MCR Format” on page 97
shows the layout of the new format. The op
code for this format lies within the coprocessor register transfer instruction type. These
instructions have their own syntax.
Two new fields were created for this format, acc and opcode_3. The acc field specifies
one of eight internal accumulators to operate on and opcode_3 defines the operation
for this format. The Intel XScale processor defines a single 40-bit accumulator referred
to as acc0; future implementations may define multiple internal accumulators. The
Intel XScale processor uses opcode_3 to define six instructions, MIA, MIAPH, MIABB,
MIABT, MIATB and MIATT.
Table 65.
Multiply with Internal Accumulate Format
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
cond
1 1 1 0 0 0 1 0
opcode_3
Rs
0 0 0 0
acc
1
Rm
Bits
Description
Notes
31:28
cond - Intel
®
StrongARM
*
condition codes
-
19:16
opcode_3 - specifies the type of multiply with
internal accumulate
Intel XScale processor defines the following:
0b0000 =
MIA
0b1000 =
MIAPH
0b1100 =
MIABB
0b1101 =
MIABT
0b1110 =
MIATB
0b1111 =
MIATT
The effect of all other encodings are
unpredictable.
15:12
Rs - Multiplier
7:5
acc - select 1 of 8 accumulators
Intel XScale processor only implements acc0;
access to any other acc has unpredictable
effect.
3:0
Rm - Multiplicand
-