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1-9 M32R-FPU Software Manual (Rev.1.01)
CPU PROGRAMMING MODEL
1.3 Control Registers
(3) Inexact Exception (IXCT)
The exception occurs when the operation result differs from a result led out with an
infinite range of precision. The following table shows the operation results and the
respective conditions in which each IXCT occurs.
Operation Result (Content of the Destination Register)
Occurrence Condition When the IXCT EIT processing is When the IXCT EIT processing is
masked (Note 1) executed (Note 2)
Overflow occurs in OVF Reference OVF operation results No change
masked condition
Rounding occurs Rounded value No change
Note 1: When the Inexact Exception Enable (EX) bit (FPSR register bit 17) = "0"
Note 2: When the Inexact Exception Enable (EX) bit (FPSR register bit 17) = "1"
(4) Zero Division Exception (DIV0)
The exception occurs when a finite nonzero value is divided by zero. The following
table shows the operation results when a DIV0 occurs.
Operation Result (Content of the Destination Register)
Dividend When the DIV0 EIT processing is When the DIV0 EIT processing is
masked (Note 1) executed (Note 2)
Nonzero finite value ±infinity (Sign is derived by exclusive- No change
ORing the signs of divisor and dividend)
Note 1: When the Zero Division Exception Enable (EZ) bit (FPSR register bit 19) = "0"
Note 2: When the Zero Division Exception Enable (EZ) bit (FPSR register bit 19) = "1"
Please note that the DIV0 EIT processing does not occur in the following conditions.
Dividend Behavior
0 An invalid operation exception occurs
infinity No exception occur (with the result "infinity")