Toshiba TX39 user manual Status register register no.12, Bits, Field name Description, Read, Write

Architecture

6.2.3Status register (register no.12)

This register holds the operating mode status (user mode or kernel mode), interrupt masking status, diagnosis status and similar information.

31

28

25

22

21

20

19 16 15

8

76

5

4

3

2

1

0

CU[3:0]

0

RE

0

BEV

T

Nml

0

IntMask

0

KUo

IEo

KUp

IEp

KUc

IEc

S

Int[5:0] Sw[1:0]

4

2

1

2

1

1

1

4

8

2

1

1

1

1

1

1

Bits

Mnemonic

Field name

Description

Value on

Read/

Reset

Write

31-28

CU

Coprocessor

The usability of the four coprocessors

Undefined

Read/

Usability

CP0 through CP3 is controlled by bits

Write

CU0 to CU3, with 1 = usable and 0 =

unusable.

25

RE

Reverse

Setting this bit in user mode reverses the

Undefined

Read/

Endian

initial setting of the endian.

Write

22

BEV†

Bootstrap

When this bit is set to 1, if a UTLB Refill

1

Read/

Exception

exception or general exception occurs,

Write

Vector

the alternate bootstrap vector (the vector

address shown in parentheses in Table

6-2) is used.

21

TS†

TLB Shutdown

This bit is set to 1 when the TLB

1

Read

becomes unusable. It is always set to 1

when the internal MMU is enabled.

20

NmI

Non-maskable

This bit is set to 1 when a non-maskable

0

Read/

Interrupt

interrupt occurs.

Writing 1 to this bit

Write

clears it to 0.

15-8

IntMask

Interrupt Mask

These are mask bits corresponding to

Undefined

Read/

hardware interrupts Int5..0 and software

Write

interrupts Sw1..0.

Here 1 = interrupt

enabled and 0 = interrupt masked.

5

KUo

Kernel/User

0

= kernel mode;

Undefined

Read/

Mode old

1

= user mode.

Write

4

IEo

Interrupt

1

= interrupt enabled;

Undefined

Read/

Enabled old

0

= interrupt masked.

Write

3

KUp

Kernel/User

0

= kernel mode;

Undefined

Read/

Mode previous

1

= user mode.

Write

2

IEp

Interrupt

1

= interrupt enabled;

Undefined

Read/

Enabled

0

= interrupt masked.

Write

previous

1

KUc

Kernel/User

0

= kernel mode;

0

Read/

Mode current

1

= user mode.

Write

0

IEc

Interrupt

1

= interrupt enabled;

0

Read/

Enabled

0

= interrupt masked.

Write

current

†Used mainly for diagnosis and testing.

53