Assembler syntax

<LDM|STM>{cond}<FD|ED|FA|EA|IA|IB|DA|DB>

Rn{!},<Rlist>{^}

where:

{cond} two character condition mnemonic. See Table 6.

Rn is an expression evaluating to a valid register number

<Rlist> is a list of registers and register ranges enclosed in {} (e.g. {R0,R2-R7,R10}).

{!} if present requests write-back (W=1), otherwise W=0

{^} if present set S bit to load the CPSR along with the PC, or force transfer of user bank when in privileged mode

Table 10. Addressing Mode Names

Addressing mode names

There are different assembler mnemonics for each of the addressing modes, depending on whether the instruction is being used to support stacks or for other purposes. The equivalence between the names and the values of the bits in the instruction are shown in the following table

FD, ED, FA, EA define pre/post indexing and the up/down bit by reference to the form of stack required. The F and E refer to a “full” or “empty” stack, i.e. whether a pre-index has to be done (full) before storing to the stack. The A and D refer to whether the stack is ascending or descending. If ascending, a STM will go up and LDM down, if descending, vice-versa.

IA, IB, DA, DB allow control when LDM/STM are not being used for stacks and simply mean Increment After, Increment Before, Decrement After, Decrement Before.