ColdFire CoreMCF5253 Reference Manual, Rev. 13-4 Freescale Semiconductor3.2.2 Enhanced Multiply Accumulate Module (eMAC) User Memory Mapand Register DescriptionThe eMAC provides a variety of program-visible registers:• Four 48-bit accumulators (Raccx = Racc0, Racc1, Racc2, Racc3)• Eight 8-bit accumulator extensions (2 per accumulator), packaged as two 32-bit values for load andstore operations (Raccext01, Raccext23)• One 16-bit Mask Register (Rmask)• One 32-bit Status Register (MACSR) including four indicator bits signaling product oraccumulation overflow (one for each accumulator: PAV0, PAV1, PAV2, PAV3)3.2.2.1 eMAC Instruction Set SummaryThe eMAC unit supports the integer multiply operations defined by the baseline ColdFire architecture, aswell as the multiply-accumulate instructions. Table 3-3 summarizes the eMAC unit instruction set.1 V Overflow condition code bit. Set if an arithmetic overflow occurs, implying that the result cannot berepresented in the operand size; otherwise cleared.0 C Carry condition code bit. Set if a carry-out of the data operand msb occurs for an addition or if a borrowoccurs in a subtraction; otherwise cleared.Table 3-3. eMAC Instruction SummaryCommand Mnemonic DescriptionMultiply Signed MULS y,Dx Multiplies two signed operands yielding a signed resultMultiply Unsigned MULU y,Dx Multiplies two unsigned operands yielding an unsigned resultMultiply Accumulate MAC Ry,RxSF,RaccxMSAC Ry,RxSF,RaccxMultiplies two operands, then adds/subtracts the product to/from anaccumulatorMultiply Accumulate withLoadMAC Ry,RxSF,Rw,RaccxMSAC Ry,RxSF,Rw,RaccxMultiplies two operands, then combines the product to anaccumulator while loading a register with the memory operandLoad Accumulator MOV.L {Ry,#imm},Raccx Loads an accumulator with a 32-bit operandStore Accumulator MOV.L Raccx,Rx Writes the contents of an accumulator to a CPU registerCopy Accumulator MOV.L Raccy,Raccx Copies a 48-bit accumulatorLoad MAC Status Reg MOV.L {Ry,#imm},MACSR Writes a value to the MAC status registerStore MAC Status Reg MOV.L MACSR,Rx Write the contents of the MAC status register to a CPU registerStore MACSR to CCR MOV.L MACSR,CCR Write the contents of the MAC status register to theprocessor’s CCR registerLoad MAC Mask Reg MOV.L {Ry,#imm},Rmask Writes a value to the MAC Mask RegisterStore MAC Mask Reg MOV.L Rmask,Rx Writes the contents of the MAC mask register to a CPUregisterTable 3-2. CCR Register Field Description (continued)Field Code Description
