SDA5523 Micronas Semiconductor, SDA5523 Datasheet - Page 42

• Manufacturer Part Number: SDA5523
• Description: SDA55xx TVText Pro
• Manufacturer: Micronas Semiconductor

SDA 55xx
2.3.13. Interrupt Nesting
The process whereby a higher-level interrupt request
interrupts a lower-level interrupt service routine is
called “nesting”.
In this case the address of the next instruction in the
lower-priority service routine is pushed onto the stack,
the stack pointer is incremented by two and the micro-
controller will continue the SW program execution from
the memory location of the first instruction of the
higher-level service routine. The last instruction of the
higher-priority interrupt service program must be a
RETI-instruction. This instruction clears the higher ‘pri-
ority-level-active’ flip-flop. The RETI command also
makes that the microcontroller executes the next
instruction of the lower-level interrupt service routine.
Since the lower ‘priority-level-active’ flip-flop has
remained set, higher priority interrupts are re-enabled
while further lower-priority interrupts remain disabled.
2.3.14. External Interrupts
The external interrupt request inputs (INT0 and INT1)
can be programmed for either transition- activated or
level-activated operation. Control of the external inter-
rupts is provided in the TCON register.
Table 2–22: Related register
42
Register Name
TCON
See Section 3. on page 110 for detailed register description.
7
TF1
6
TR1
5
TF0
Sept. 10, 2004; 6251-556-3DS
4
TR0
Bit Name
3
IE1
2
IT1
1
IE0
DATA SHEET
0
IT0
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