RX610 Group
2. CPU
R01UH0032EJ0120 Rev.1.20
Page 64 of 1006
Feb 20, 2013
FV Flag (Invalid Operation flag), FO Flag (Overflow Flag), FZ Flag (Division-by-Zero Flag),
FU Flag (Underflow Flag), and FX Flag (Inexact Flag)
While the exception handling enable bit (Ej) is 0 (exception handling is masked), if any of five floating-point exceptions
specified in the IEEE754 standard is generated, the corresponding bit is set to 1.
• When Ej is 1 (exception handling is enabled), the value of the flag remains.
• When the corresponding flag is set to 1, it remains 1 until it is cleared to 0 by software. (Accumulation flag)
FS Flag (Floating-Point Error Summary Flag)
This bit reflects the logical OR of the FU, FZ, FO, and FV flags.
2.2.2.9
Accumulator (ACC)
b63
Value after reset:
Undefined
b48 b47
b32 b31
b16 b15
b0
Range for reading and writing by
MVTACHI and MVFACHI
Range for writing by MVTACLO
Range for reading by MVFACMI
The accumulator (ACC) is a 64-bit register used for DSP instructions. The accumulator is also used for the multiply and
multiply-and-accumulate instructions; EMUL, EMULU, FMUL, MUL, and RMPA, in which case the prior value in the
accumulator is modified by execution of the instruction.
Use the MVTACHI and MVTACLO instructions for writing to the accumulator. The MVTACHI and MVTACLO
instructions write data to the higher-order 32 bits (bits 63 to 32) and the lower-order 32 bits (bits 31 to 0), respectively.
Use the MVFACHI and MVFACMI instructions for reading data from the accumulator. The MVFACHI and MVFACMI
instructions read data from the higher-order 32 bits (bits 63 to 32) and the middle 32 bits (bits 47 to 16), respectively.