32 bit rules



For those interested in what the S bit does in 32bit mode...

Any 32-bit write to R15 with the S bit set (MOVS, ORRS, TEQP, LDM...^) will transfer the SPSR for the current mode to the CPSR.
For example, assuming we are in irq_32 mode:

  MOVS PC, R14
would copy R14 to PC, and then copy SPSR_IRQ32 to CPSR.

This is not terribly useful as USR mode does not even have an SPSR!


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Copyright © 2001 Richard Murray