AT697F_14 datasheet(98/176 Pages) ATMEL

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AT697F

7703E–AERO–08/11

Floating-Point Trap Types - ftt

Table 40. Trap Type Definition

none

No trap.

IEEE_754_exception

An IEEE_754_exception floating-point trap type indicates that a floating-point exception

occurred that conforms to the ANSI/IEEE Standard 754-1985. The exception type is encoded in the

cexc field.

reserved

sequence_error

A sequence_error indicates one of three abnormal error conditions in the FPU, all caused by

erroneous supervisor software:

•

An attempt was made to execute a floating-point instruction when the FPU was not

able to accept one. This type of sequence_error arises from a logic error in

supervisor software that has caused a previous floating-point trap to be incompletely

serviced (for example, the floating-point queue was not emptied after a previous

floating-point exception).

•

An attempt was made to execute a STDFQ instruction when the floating-point

deferred-trap queue (FQ) was empty, that is, when FSR.qne = 0. (Note that

generation of sequence_error is recommended, but not required in this case)

reserved

Floating-Point Condition Code

- fcc

Table 41. fcc Field Definition

frs1 = frs2

frs1 < frs2

frs1 > frs2

frs1 ? frs2

Indicates an unordered relation, which is true if either frs1 or frs2 is a signaling NaN or quiet NaN

Note:

frs1 and frs2 correspond to the single, double, or quad values in the f registers specified by

an instruction’s rs1 and rs2 fields. Note that fcc is unchanged if FCMP or FCMPE gener-

ate an IEEE_754_exception trap.

Floating-Point Exception

Fields - aexc / cexc

The accrued and current exception fields and the trap enable mask assume the follow-

ing definitions of the floating-point exception conditions.

Table 42. Exception Fields

ftt

Name

Description

fcc

Description

Aexc Mnemonic Cexc Mnemonic

Name

Description

nva

nvc

Invalid

An operand is improper for the operation to be performed (1 = invalid

operand, 0 = valid operand(s)).

Examples: 0 ÷ 0, ∞ - ∞ are invalid.

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