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THUMB INSTRUCTION SET S3C2440A RISC MICROPROCESSOR
4-28
FORMAT 12: LOAD ADDRESS
[7:0] 8-bit Unsigned Constant
[10:8] Destination Register
[11] Source
0 = PC
1 = SP
15 0
1
14
10
01
13 12
11
Word 8
0 SP Rd
78
Figure 4-13. Format 12
OPERATION
These instructions calculate an address by adding a 10-bit constant to either the PC or the SP, and load the
resulting address into a register. The THUMB assembler syntax is shown in the following table.
Table 4-13. Load Address
L THUMB assembler ARM equivalent Description
0 ADD Rd, PC, #Imm ADD Rd, R15, #Imm Add #Imm to the current value of the
program counter (PC) and load the result
into Rd.
1 ADD Rd, SP, #Imm ADD Rd, R13, #Imm Add #Imm to the current value of the stack
pointer (SP) and load the result into Rd.
NOTE
The value specified by #Imm is a full 10-bit value, but this must be word-aligned (ie with bits 1:0 set to 0)
since the assembler places #Imm >> 2 in field Word 8.
Where the PC is used as the source register (SP = 0), bit 1 of the PC is always read as 0. The value of the PC will
be 4 bytes greater than the address of the instruction before bit 1 is forced to 0.
The CPSR condition codes are unaffected by these instructions.