![](http://datasheet.mmic.net.cn/110000/M32186F8VFP_datasheet_3496152/M32186F8VFP_105.png)
4
EIT
4-3
32185/32186 Group Hardware Manual
Rev.1.10 REJ09B0235-0110 May 15, 07
4.2 EIT Events
4.2.1 Exception
(1) Reserved Instruction Exception (RIE)
Reserved Instruction Exception (RIE) occurs when execution of a reserved instruction (unimplemented
instruction) is detected.
(2) Address Exception (AE)
Address Exception (AE) occurs when an attempt is made to access a misaligned address in Load or
Store instructions.
(3) Floating-point Exception (FPE)
Floating-point Exception (FPE) occurs when Unimplemented Exception (UIPL) or one of the five ex-
ceptions specified in the IEEE 754 standard (OVF/UDF/IXCT/DIV0/IVLD) is detected. Each exception
processing is outlined below.
1) Overflow Exception (OVF)
The exception occurs when the absolute value of the operation result exceeds the largest describable
precision in the floating-point format. The following table shows the operation results when an OVF occurs.
Table 4.2.1 Operation Results When an OVF Occurred
Note 1: When the overflow exception enable (EO) bit (FPSR register bit 20) = "0"
Note 2: When the overflow exception enable (EO) bit (FPSR register bit 20) = "1"
Notes: If an OVF occurs while EIT processing for OVF is masked, an IXCT occurs at the same time.
+MAX = H’7F7F FFFF, –MAX = H’FF7F FFFF
2) Underflow Exception (UDF)
The exception occurs when the absolute value of the operation result is less than the largest
describable precision in the floating-point format. The following table shows the operation results
when a UDF occurs.
Table 4.2.2 Operation Results when a UDF Occurred
Note 1: When the underflow exception enable (EU) bit (FPSR register bit 18) = "0"
Note 2: When the underflow exception enable (EU) bit (FPSR register bit 18) = "1"
Rounding Mode
Sign of the Result
Operation Result (Content of the Destination Register)
When the OVF EIT processing is
masked (Note 1)
executed (Note 2)
-Infinity
+
+MAX
-
-Infinity
+Infinity
+
+Infinity
-
-MAX
No Change
0
+
+MAX
-
-MAX
Nearest
+
+Infinity
-
-Infinity
Operation Result (Content of the Destination Register)
When UDF EIT processing is masked (Note 1)
When UDF EIT processing is executed (Note 2)
DN = 0 : An unimplemented exception occurs
No change