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16-bit signed
PC index
Program
counter PC
16-bit signed add
0
Memory address
FFFFF
00000
Lo
wer 64 KB
0FFFF
10000
PC.19:0
Lower 64 KB
PC.19:16 = 0
16-bit byte index
0
19 16 15
0
S
Addressing Modes
Figure 4-19. Symbolic Mode Running in Lower 64 KB
Operation:
The signed 16-bit index in the next word after the instruction is added temporarily to
the PC. The resulting bits 19:16 are cleared giving a truncated 16-bit memory
address, which points to an operand address in the range 00000h to 0FFFFh. The
operand is the content of the addressed memory location.
Length:
Two or three words
Comment:
Valid for source and destination. The assembler calculates the PC index and
inserts it.
ADD.B EDE,TONI ;
Example:
This instruction adds the 8-bit data contained in source byte EDE and destination
byte TONI and places the result into the destination byte TONI. Bytes EDE and
TONI and the program are located in the lower 64 KB.
Source:
Byte EDE located at address 0579Ch, pointed to by PC + 4766h, where the PC
index 4766h is the result of 0579Ch – 01036h = 04766h. Address 01036h is the
location of the index for this example.
Destination:
Byte TONI located at address 00778h, pointed to by PC + F740h, is the truncated
16-bit result of 00778h – 1038h = FF740h. Address 01038h is the location of the
index for this example.
104
CPUX
SLAU272C – May 2011 – Revised November 2013
Copyright © 2011–2013, Texas Instruments Incorporated