P8044AH-R0117 datasheet(35/65 Pages) INNOVASIC

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IA8044/IA8344

Data Sheet

SDLC Communications Controller

March 30, 2010

IA211010112-04

http://www.Innovasic.com

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Page 35 of 65

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4.9.5

Interrupt Handling

The interrupt flags are sampled during each machine cycle. The samples are polled during the

next machine cycle. If an interrupt flag is captured, the interrupt system will generate an LCALL

instruction to the appropriate service routine, provided that this is not disabled by the following

conditions:

An interrupt of the same or higher priority is processed.

The current machine cycle is not the last cycle of the instruction (the instruction cannot be

interrupted).

The instruction in progress is RETI or any write to IE or IP registers.

Note: If an interrupt is disabled and the interrupt flag is cleared before the

blocking condition is removed, no interrupt will be generated because the

polling cycle will not sample any active interrupt condition. In other words,

the interrupt condition is not remembered; every polling cycle is new.

4.9.6

Interrupt Priority Register (IP)

This register sets the interrupt priority to high or low for each interrupt. When the bit is set, it

selects high priority. Within each level the interrupts are prioritized as follows:

External Interrupt 0

Timer/Counter 0

External Interrupt 1

Timer/Counter 1

SIU

An interrupt process routine cannot be interrupted by an interrupt of lesser or equal priority (see

Table 29).

Table 29. Interrupt Priority Register

–

PT1

PX1

PT0

PX0

Bit [7]—(IP.7)

Bit [6]—(IP.6)

Bit [5]—(IP.5)

Bit [4]—PS → (IP.4) SIU interrupt priority bit

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