Assembler Reference

LDC, LDC2, STC, and STC2

ARM Compiler toolchain v5.02 for µVision Assembler Reference

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Transfer Data between memory and Coprocessor.

op{L}{cond} coproc, CRd, [Rn]

op{L}{cond} coproc, CRd, [Rn, #{-}offset]   ; offset addressing

op{L}{cond} coproc, CRd, [Rn, #{-}offset]!  ; pre-index addressing

op{L}{cond} coproc, CRd, [Rn], #{-}offset    ; post-index addressing

op{L}{cond} coproc, CRd, label

where:

op: is one of LDC, LDC2, STC, or STC2.
cond: is an optional condition code.
In ARM code, cond is not permitted for LDC2 or STC2.
L: is an optional suffix specifying a long transfer.
coproc: is the name of the coprocessor the instruction is for. The standard name is pn, where n is an integer in the range 0 to 15.
CRd: is the coprocessor register to load or store.
Rn: is the register on which the memory address is based. If PC is specified, the value used is the address of the current instruction plus eight.
-: is an optional minus sign. If - is present, the offset is subtracted from Rn. Otherwise, the offset is added to Rn.
offset: is an expression evaluating to a multiple of 4, in the range 0 to 1020.
!: is an optional suffix. If ! is present, the address including the offset is written back into Rn.
label: is a word-aligned PC-relative expression.
label must be within 1020 bytes of the current instruction.

The use of these instructions depends on the coprocessor. See the coprocessor documentation for details.

In ThumbEE, if the value in the base register is zero, execution branches to the NullCheck handler at HandlerBase - 4.

LDC and STC are available in all versions of the ARM architecture.

LDC2 and STC2 are available in ARMv5T and above.

These 32-bit Thumb instructions are available in ARMv6T2 and above.

There are no 16-bit Thumb versions of these instructions.

You cannot use PC for Rn in the pre-index and post-index instructions. These are the forms that write back to Rn.

You cannot use PC for Rn in Thumb STC and STC2 instructions.

ARM STC and STC2 instructions that use the label syntax, or where Rn is PC, are deprecated in ARMv6T2 and above.