UM0438 datasheet(21/50 Pages) STMICROELECTRONICS

21 / 50 page

UM0438

Instruction set

21/50

The VLE extension does not currently fully encompass 64-bit operations, although the

addition of such operations in a future version is envisioned. For future compatibility, and to

avoid confusion with Book E, register bit numbering remains the same as in traditional

Book E.

The description of each instruction is contained in the VLE section of the EREF and includes

the mnemonic and a formatted list of operands. VLE instructions have either exact or similar

semantics to Book E instructions. Where the semantics, side-effects, and binary encodings

are identical, the Book E mnemonics and formats are used. Where the semantics are

similar but the binary encodings differ, the Book E mnemonic is generally preceded with an

‘e_’. To distinguish similar instructions available in both 16- and 32-bit formats under VLE

and standard Book E instructions, VLE instructions encoded with 16 bits have an ‘se_’

prefix. VLE instructions encoded with 32 bits that have different binary encodings or

semantics than the equivalent Book E instruction have an ‘e_’ prefix. Some examples are

the following:

stw RS,D(RA) // Standard Book E instruction

e_stw RS,D(RA) // 32-bit VLE instruction

se_stw RZ,SD4(RX)// 16-bit VLE instruction

For detailed functional descriptions of each VLE instruction, along with the assembly

mnemonic and operands, refer to the VLE section of the EREF.

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