UM0438 datasheet(39/50 Pages) STMICROELECTRONICS

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UM0438

Simplified mnemonics for VLE instructions

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A.8

Simplified mnemonics for accessing SPRs

The mtspr and mfspr instructions specify a special-purpose register (SPR) as a numeric

operand. Simplified mnemonics are provided that represent the SPR in the mnemonic rather

than requiring it to be coded as a numeric operand. The pattern for mtspr and mfspr

simplified mnemonics is straightforward: replace the -spr portion of the mnemonic with the

abbreviation for the spr (for example XER, SRR0, or LR), eliminate the SPRN operand,

leaving the source or destination GPR operand, rS or rD.

Following are examples using the SPR simplified mnemonics:

Copy the contents of rS to the XER.

mtxer rS

equivalent to

mtspr 1,rS

Copy the contents of the LR to rS.

mflr rD

equivalent to

mfspr rD,8

Copy the contents of rS to the CTR.

mtctr rS

equivalent to

mtspr 9,rS

The examples above show simplified mnemonics for accessing SPRs defined by the AIM

version of the PowerPC architecture; however, the same formula is used for Book E, EIS,

and implementation-specific SPRs, as shown in the following examples:

Copy the contents of rS to CSRR0.

mtcsrr0 rS

equivalent to

mtspr 58,rS

Copy the contents of IVOR0 to rS.

mfivor0 rD

equivalent to

mfspr rD,400

Copy the contents of rS to the MAS1.

mtmas1 rS

equivalent to

mtspr 625,rS

There are additional simplified mnemonics for accessing SPRGs, which are not all

supported by all assemblers. These mnemonics are shown in Table 31 along with the

equivalent simplified mnemonic using the formula described in this section.

Table 31.

Additional simplified mnemonics for Accessing SPRGs

SPR

Move to SPR

Move from SPR

Simplified mnemonic

Equivalent to

Simplified mnemonic

Equivalent to

SPRGs

mtsprg n,rS

mtspr 272 + n,rS

mfsprg rD,n

mfspr rD,272 + n

mtsprgn,rS

mfsprgn rD

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