Freescale Semiconductor ColdFire MCF52210 - Manual (Page 84)

Multiply-Accumulate Unit (MAC)
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
4-8 Freescale Semiconductor
int macsr;
} macState;
The following assembly language routine shows the proper sequence for a correct MAC state save. This
code assumes all Dn and An registers are available for use, and the memory location of the state save is
defined by A7.
MAC_state_save:
move.l macsr,d7 ; save the macsr
clr.l d0 ; zero the register to ...
move.l d0,macsr ; disable rounding in the macsr
move.l acc,d5; save the accumulator
move.l mask,d6 ; save the address mask
movem.l #0x00e0,(a7); move the state to memory
This code performs the MAC state restore:
MAC_state_restore:
movem.l (a7),#0x00e0; restore the state from memory
move.l #0,macsr ; disable rounding in the macsr
move.l d5,acc; restore the accumulator
move.l d6,mask ; restore the address mask
move.l d7,macsr ; restore the macsr
Executing this sequence type can correctly save and restore the exact state of the MAC programming
model.
4.3.1.3 MULS/MULU
MULS and MULU are unaffected by fractional-mode operation; operands remain assumed to be integers.
4.3.1.4 Scale Factor in MAC or MSAC Instructions
The scale factor is ignored while the MAC is in fractional mode.
4.3.2 MAC Instruction Set Summary
Table 4-6 summarizes MAC unit instructions.
Table 4-6. MAC Instruction Summary
Command Mnemonic Description
Multiply Signed muls <ea>y,Dx Multiplies two signed operands yielding a signed result
Multiply Unsigned mulu <ea>y,Dx Multiplies two unsigned operands yielding an unsigned result
Multiply Accumulate mac Ry,RxSF
msac Ry,RxSF
Multiplies two operands, then adds/subtracts the product
to/from the accumulator
Multiply Accumulate
with Load mac Ry,RxSF,Rw
msac Ry,RxSF,Rw
Multiplies two operands, combines the product to the
accumulator while loading a register with the memory
operand
Load Accumulator move.l {Ry,#imm},ACC Loads the accumulator with a 32-bit operand
Store Accumulator move.l ACC,Rx Writes the contents of the accumulator to a CPU register