UPSD3254 STMICROELECTRONICS [STMicroelectronics], UPSD3254 Datasheet - Page 42

• Manufacturer Part Number: UPSD3254
• Description: Flash Programmable System Devices with 8032 Microcontroller Core
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV
Table 18. SFR Register
Interrupt Priority Structure
Each interrupt source can be assigned one of two
priority levels. Interrupt priority levels are defined
by the interrupt priority special function register IP
and IPA.
0 = low priority
1 = high priority
A low priority interrupt may be interrupted by a
high priority interrupt level interrupt. A high priority
interrupt routine cannot be interrupted by any oth-
er interrupt source. If two interrupts of different pri-
ority occur simultaneously, the high priority level
request is serviced. If requests of the same priority
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 se-
quence.
Interrupts Enable Structure
Each interrupt source can be individually enabled
or disabled by setting or clearing a bit in the inter-
rupt enable special function register IE and IEA. All
Table 20. Description of the IE Bits
42/175
Addr
SFR
A7
A8
B7
B8
Bit
7
6
5
4
3
2
1
0
Name
Reg
IEA
IPA
IE
IP
Symbol
EDDC
PDDC
EX1
EX0
ET2
ET1
ET0
EA
ES
EA
—
—
7
Disable all interrupts:
0: no interrupt with be acknowledged
1: each interrupt source is individually enabled or disabled by setting or clearing its
enable bit
Reserved
Enable Timer 2 Interrupt
Enable USART Interrupt
Enable Timer 1 Interrupt
Enable External Interrupt (Int1)
Enable Timer 0 Interrupt
Enable External Interrupt (Int0)
—
—
—
—
6
ET2
PT2
—
—
5
Bit Register Name
ES2
PS2
ES
PS
4
ET1
PT1
—
—
interrupt source can also be globally disabled by
clearing Bit EA in IE.
Table 19. Priority Levels
3
Timer 2+EXF2
2nd USART
1st USART
Function
EX1
PX1
Source
Timer 0
Timer 1
—
—
DDC
2
USB
Int0
Int1
I²C
EI
PI
ET0
PT0
1
2
2
C
C
EUSB
PUSB
EX0
PX0
0
Priority with Level
0 (highest)
9 (lowest)
Reset
Value
00
00
00
00
1
2
3
4
5
6
7
8
Enable (2nd)
Priority (2nd)
Comments
Interrupt
Interrupt
Interrupt
Interrupt
Enable
Priority