Control Register File Extensions

2.8.2Floating-Point Auxiliary Configuration Register (FAUCR)

The floating-point auxiliary register (FAUCR) contains fields that specify underflow or overflow, the rounding mode, NaNs, denormalized numbers, and inexact results for instructions that use the .S functional units. FAUCR has a set of fields specific to each of the .S units: .S2 uses bits 31−16 and .S1 uses bits 15−0. FAUCR is shown in Figure 2−15 and described in Table 2−15.

Note:

For the C67x+ DSP, the ADDSP, ADDDP, SUBSP, and SUBDP instructions executing in the .S functional unit use the rounding mode from and set the warning bits in the floating-point adder configuration register (FADCR). The warning bits in FADCR are the logical-OR of the warnings produced on the

.L functional unit and the warnings produced by the ADDSP/ADDDP/ SUBSP/SUBDP instructions on the .S functional unit (but not other instruc- tions executing on the .S functional unit).

Figure 2−15. Floating-Point Auxiliary Configuration Register (FAUCR)

31

27

26

25

24

23

22

21

20

19

18

17

16

 

 

 

 

 

 

 

 

 

 

 

 

 

Reserved

 

DIV0

UNORD

UND

INEX

OVER

INFO

INVAL

DEN2

DEN1

NAN2

NAN1

 

 

 

 

 

 

 

 

 

 

 

 

 

R-0

 

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

15

11

10

9

8

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

Reserved

 

DIV0

UNORD

UND

INEX

OVER

INFO

INVAL

DEN2

DEN1

NAN2

NAN1

 

 

 

 

 

 

 

 

 

 

 

 

 

R-0

 

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

Legend: R = Readable by the MVC instruction; W = Writeable by the MVC instruction; -n= value after reset

Table 2−15. Floating-Point Auxiliary Configuration Register (FAUCR) Field Descriptions

Bit

Field

Value

Description

 

 

 

 

31−27

Reserved

0

Reserved. The reserved bit location is always read as 0. A value written to this

 

 

 

field has no effect.

 

 

 

 

26

DIV0

 

Source to reciprocal operation for .S2.

 

 

0

0 is not source to reciprocal operation.

 

 

1

0 is source to reciprocal operation.

 

 

 

 

SPRU733

CPU Data Paths and Control

2-27

Page 53
Image 53
Texas Instruments TMS320C67X/C67X+ DSP manual Floating-Point Auxiliary Configuration Register Faucr