MOTOROLA
Chapter 3. Enhanced Multiply-Accumulate Unit (EMAC)
3-13
EMAC Instruction Set Summary
The mov.l instruction that stores the accumulator to an integer register (Rz) stalls until the
program-visible copy of the accumulator is available. Figure 3-8 shows EMAC timing.
Figure 3-8. EMAC-Specific OEP Sequence Stall
In Figure 3-8, the OEP stalls the store-accumulator instruction for 3 cycles: the depth of the
EMAC pipeline minus 1. The minus 1 factor is needed because the OEP and EMAC
pipelines overlap by a cycle, the AGEX stage. As the store-accumulator instruction reaches
the AGEX stage where the operation is performed, the just-updated accumulator 0 value is
available.
As with change or use stalls between accumulators and general-purpose registers,
introducing intervening instructions that do not reference the busy register can reduce or
eliminate sequence-related store-MAC instruction stalls. In fact, a major benefit of the
EMAC is the addition of three accumulators to minimize stalls caused by exchanges
between the accumulator(s) and the general-purpose registers.
3.5.2
Data Representation
MACSR[S/U,F/I] selects one of the following three modes, where each mode defines a
unique operand type.
• Two’s complement signed integer: In this format, an N-bit operand value lies in the
range -2
(N-1)
< operand < 2
(N-1)
- 1. The binary point is right of the lsb.
• Unsigned integer: In this format, an N-bit operand value lies in the range 0 < operand
< 2
N
- 1. The binary point is right of the lsb.
• Two’s complement, signed fractional: In an N-bit number, the first bit is the sign bit.
The remaining bits signify the first N-1 bits after the binary point. Given an N-bit
number,
a
N-1
a
N-2
a
N-3
... a
2
a
1
a
0
, its value is given by the equation in Figure 3-9.
DSOC
AGEX
mac
mac
EMAC EX1
EMAC EX2
EMAC EX3
EMAC EX4
mac
mac
mac
mac
mov
mov
mov
mov
Three-cycle
regBusy stall
Accumulator 0
old
new
Содержание ColdFire MCF5281
Страница 1: ...MCF5282UM D Rev 2 1 2004 MCF5282 ColdFire Microcontroller User s Manual Devices Supported MCF5281 ...
Страница 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Страница 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Страница 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Страница 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Страница 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Страница 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Страница 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Страница 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Страница 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Страница 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Страница 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Страница 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Страница 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Страница 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Страница 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Страница 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Страница 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Страница 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Страница 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Страница 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Страница 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Страница 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...
Страница 800: ...A 22 MCF5282 User s Manual MOTOROLA ...