3.9. Implementation-defined Behaviour of Instructions

The ARM Architectural Reference Manual defines the instruction set of the ARM720T. The following list defines the behaviour of the ARM720T instructions for those features which are denoted as being implementation defined in that manual.

Indexed Addressing on a Data abort

For the following instructions:

  • LDC

  • LDM

  • LDR

  • LDRB

  • LDRBT

  • LDRH

  • LDRSB

  • LDRSH

  • LDRT

in the event of a data abort with pre-indexed or post-indexed addressing, the value left in Rn is defined to be the updated base register value.

For the following instructions:

  • STC

  • STM

  • STR

  • STRB

  • STRBT

  • STRH

  • STRT

in the event of a data abort with pre-indexed or post-indexed addressing, the value left in Rn is defined to be the updated base register value.

Early Termination

On the ARM720T, early termination is defined as:

MLA, MUL               signed early termination.

SMULL, SMLAL      signed early termination.

UMULL, UMLAL      unsigned early termination.

Copyright © 1997, 1998 ARM Limited. All rights reserved.DDI 0087E
Non-Confidential