CPU Registers
4-20
16-Bit MSP430X CPU
MSP430 Instruction with Indexed Mode in Upper Memory
If the CPU register Rn points to an address above the lower 64-KB memory,
the Rn bits 19:16 are used for the address calculation of the operand. The
operand may be located in memory in the range Rn
±
32 KB, because the
index, X, is a signed 16-bit value. In this case, the address of the operand can
overflow or underflow into the lower 64-KB memory space. See Figure 4−16
and Figure 4−17.
Figure 4−16. Indexed Mode in Upper Memory
16-bit signed index
(sign extended to
20 bits)
CPU Register
Rn
20-bit signed add
Memory address
FFFFF
00000
Lower 64 KB
0FFFF
10000
Upper Memory
Rn.19:16 > 0
16-bit byte index
1 ... 15
19
16 15
0
S
Rn
±
32 KB
S
Rn.19:0
Figure 4−17. Overflow and Underflow for the Indexed Mode
ÇÇÇÇÇÇ
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ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
FFFFF
0000C
Lower
64 KB
0,FFFF
10000
Rn.19:0
Rn.19:0
Rn.19:0
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
±
32KB
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
ÇÇÇÇÇÇ
±
32KB
Rn.19:0
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 ...