
2100h
Address
Space
2346h
55D6h
PC
21038h
21036h
21034h
23456h
45678h
R5
R6
45678h
+32100h
77778h
Register
Before:
Address
Space
Register
After:
PC
23456h
45678h
R5
R6
0001h
2345h
7777Ah
77778h
0007h
7777h
7777Ah
77778h
65432h
+12345h
77777h
src
dst
Sum
0006h
5432h
3579Eh
3579Ch
0006h
5432h
3579Eh
3579Ch
1883h
21032h
xxxxh
2103Ah
2100h
2346h
55D6h
21038h
21036h
21034h
1883h
21032h
xxxxh
2103Ah
23456h
+12346h
3579Ch
Addressing Modes
The extension word contains the MSBs of the source index and of the destination index and the A/L bit for
20-bit data. The instruction word uses byte mode due to the 20-bit data length with bits A/L:B/W = 01.
4.4.3 Symbolic Mode
The Symbolic mode calculates the address of the operand by adding the signed index to the PC. The
Symbolic mode has three addressing possibilities:
•
Symbolic mode in lower 64-KB memory
•
MSP430 instruction with Symbolic mode addressing memory above the lower 64-KB memory.
•
MSP430X instruction with Symbolic mode
4.4.3.1
Symbolic Mode in Lower 64 KB
If the PC points to an address in the lower 64 KB of the memory range, the calculated memory address
bits 19:16 are cleared after the addition of the PC and the signed 16-bit index. This means the calculated
memory address is always located in the lower 64 KB and does not overflow or underflow out of the lower
64-KB memory space. The RAM and the peripheral registers can be accessed this way and existing
MSP430 software is usable without modifications as shown in
103
SLAU272C – May 2011 – Revised November 2013
CPUX
Copyright © 2011–2013, Texas Instruments Incorporated