Rev. C - 15 January, 2001

19

TS80C31X2

Table 7. Priority Level Bit Values

A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-priority interrupt.

A high-priority interrupt can’t be interrupted by any other interrupt source.

If two interrupt requests of different priority levels are received simultaneously, the request of higher priority level

is serviced. If interrupt requests of the same priority level are received simultaneously, an internal polling sequence

determines which request is serviced. Thus within each priority level there is a second priority structure determined

by the polling sequence.

Table 8. IE Register

IE - Interrupt Enable Register (A8h)

Reset Value = 0XX0 0000b

Bit addressable

Table 9. IP Register

IPH.x

IP.x

Interrupt Level Priority

0

0

0 (Lowest)

0

1

1

1

0

2

1

1

3 (Highest)

7

6

5

4

3

2

1

0

EA

-

-

ES

ET1

EX1

ET0

EX0

Bit

Number

Bit

Mnemonic

Description

7

EA

Enable All interrupt bit

Clear to disable all interrupts.

Set to enable all interrupts.

If EA=1, each interrupt source is individually enabled or disabled by setting or clearing its own interrupt

enable bit.

6

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

5

-

Reserved

The value read from this bit is indeterminate. Do not set this bit.

4

ES

Serial port Enable bit

Clear to disable serial port interrupt.

Set to enable serial port interrupt.

3

ET1

Timer 1 overflow interrupt Enable bit

Clear to disable timer 1 overflow interrupt.

Set to enable timer 1 overflow interrupt.

2

EX1

External interrupt 1 Enable bit

Clear to disable external interrupt 1.

Set to enable external interrupt 1.

1

ET0

Timer 0 overflow interrupt Enable bit

Clear to disable timer 0 overflow interrupt.

Set to enable timer 0 overflow interrupt.

0

EX0

External interrupt 0 Enable bit

Clear to disable external interrupt 0.

Set to enable external interrupt 0.