32-Bit Hardware Multiplier Operation
9-17
32-Bit Hardware Multiplier
Even though the result registers were loaded with all zeros the final result is
saturated. This is because the MPYC bit was set causing the result used for
the multiply-and-accumulate to be saturated to 08000 0000h. Adding a
negative number to it would again cause an underflow thus the final result is
also saturated to 08000 0000h.
9.2.6
Indirect Addressing of Result Registers
When using indirect or indirect autoincrement addressing mode to access the
result registers and the multiplier requires 3 cycles until result availability
according to Table 9−1, at least one instruction is needed between loading the
second operand and accessing the result registers:
; Access multiplier 16x16 results with indirect addressing
MOV
#RES0,R5
; RES0 address in R5 for indirect
MOV
&OPER1,&MPY
; Load 1st operand
MOV
&OPER2,&OP2
; Load 2nd operand
NOP
; Need one cycle
MOV
@R5+,&xxx
; Move RES0
MOV
@R5,&xxx
; Move RES1
In case of a 32x16 multiplication there is also one instruction required between
reading the first result register RES0 and the second result register RES1:
; Access multiplier 32x16 results with indirect addressing
MOV
#RES0,R5
; RES0 address in R5 for indirect
MOV
&OPER1L,&MPY32L ; Load low word of 1st operand
MOV
&OPER1H,&MPY32H ; Load high word of 1st operand
MOV
&OPER2,&OP2
; Load 2nd operand (16 bits)
NOP
; Need one cycle
MOV
@R5+,&xxx
; Move RES0
NOP
; Need one additional cycle
MOV
@R5,&xxx
; Move RES1
; No additional cycles required!
MOV
@R5,&xxx
; Move RES2
Summary of Contents for MSP430x4xx Family
Page 1: ...MSP430x4xx Family 2007 Mixed Signal Products User s Guide SLAU056G ...
Page 2: ......
Page 6: ...vi ...
Page 114: ...3 76 RISC 16 Bit CPU ...
Page 304: ...5 20 FLL Clock Module ...
Page 340: ...7 8 Supply Voltage Supervisor ...
Page 348: ...8 8 16 Bit Hardware Multiplier ...
Page 372: ...9 24 32 Bit Hardware Multiplier ...
Page 400: ...10 28 DMA Controller ...
Page 428: ...13 10 Basic Timer1 ...
Page 466: ...15 24 Timer_A ...
Page 522: ...17 30 USART Peripheral Interface UART Mode ...
Page 544: ...18 22 USART Peripheral Interface SPI Mode ...
Page 672: ...23 12 Comparator_A ...
Page 692: ...24 20 LCD Controller ...
Page 746: ...26 28 ADC12 ...