_ReadCoProcessor (Windows Embedded CE 6.0)

1/5/2010

This instruction causes the specified coprocessor registers to transfer values to two ARM registers.

Syntax

__int64 _ReadCoProcessor(
  int Arg1
);

Parameters

• Arg1
  [in] Coprocessor number, equivalent to cp_num.

Return Values

Value held in coprocessor register.

Remarks

The compiler translates this instruction into the MRRC assembly instruction for ARM DSP-enhanced processors, and into the MRA assembly instruction for ARM XScale processors. MRA is disassembled as the MRCC instruction.

The XScale and the DSP-enhanced ARM microprocessors each implement this instruction in a different way:

• For the ARM XScale implementation, this instruction does the following:
  • Moves 64 bits of data to ARM registers from Coprocessor registers
  • Moves the 40-bit accumulator value (acc0) into two registers
  • Moves bits [31:0] of the value in acc0 into the register RdLo
  • Sign-extends bits [39:32] of the value in acc0 to 32 bits and moves them into the register RdHi
• For the ARM DSP-enhanced implementation, this instruction causes the coprocessor to transfer values to the two general-purpose registers Rd and Rn.

Requirements

See Also

Reference

ARM DSP-enhanced Intrinsic Functions
ARM XSCALE Intrinsic Functions
_WriteCoProcessor