Freescale Semiconductor SC140 specifications Exception and Mode Register EMR

Models: SC140

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Core Control Registers

 

 

 

 

 

 

 

 

Table 3-1. Status Register Description (Continued)

 

 

 

 

 

 

 

Name

Description

Settings

 

 

 

 

 

 

 

 

 

 

 

 

C

Carry Bit — Indicates whether a carry is

0 = No carry or borrow generated

 

 

Bit 0

generated from the resulting most

1 = Carry generated from last addition, or borrow generated

 

 

 

significant bits (MSB) of the last addition

from last subtraction

 

 

 

operation or a borrow generated in the

 

 

 

 

last subtraction operation. The carry or

 

 

 

 

borrow is generated from bit 39 of the

 

 

 

 

result. The carry bit is also affected by

 

 

 

 

DALU bit manipulation as well as rotate

 

 

 

 

and shift instructions. The carry bit

 

 

 

 

usually holds the value of the last shifted

 

 

 

 

bit.

 

 

 

 

If more than one instruction in an

 

 

 

 

execution set affects the carry bit

 

 

 

 

(according to the instruction definition),

 

 

 

 

then the carry bit is updated by the last

 

 

 

 

instruction (in assembly source order)

 

 

 

 

that actually executes, while the other

 

 

 

 

instructions do not affect the carry bit. If

 

 

 

 

no carry-affecting instructions execute,

 

 

 

 

the carry bit is not affected.

 

 

 

 

This bit is cleared during core reset as

 

 

 

 

well as at the start of an exception

 

 

 

 

service routine.

 

 

 

 

 

 

 

3.1.2 Exception and Mode Register (EMR)

The purpose of the EMR is to reflect and control exception situations in the core. EMR bits reflect memory configuration as well as the servicing of non-maskable interrupts. EMR bits also reflect exception conditions such as:

DALU overflow

EOnCE and software debugging access and control

Illegal execution set

Illegal instruction opcode

Figure 3-2 displays the bit configuration of the execution and mode register.

 

BIT 31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GP6

GP5

GP4

GP3

GP2

GP1

GP0

BEM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TYPE

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

RESET

0

0

0

0

0

0

0

0

IO

IO

IO

IO

IO

IO

IO

IO

 

BIT 15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

BIT 0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NMID

DOVF

ILST

ILIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TYPE

r

r

r

r

r

r

r

r

r

r

r

r

rw

rw

rw

rw

RESET

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Figure 3-2. Exception and Mode Register (EMR)

SC140 DSP Core Reference Manual

3-7

Page 107
Image 107
Freescale Semiconductor SC140 specifications Exception and Mode Register EMR