ST52T400 datasheet(37/94 Pages) STMICROELECTRONICS

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ST52T400/T440/E440/T441

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4 INTERRUPTS

The Control Unit (CU) responds to peripheral

events and external events via its interrupt chan-

nels.

When such an events occur, if the related interrupt

is not masked and according to a priority order,

the current program execution can be suspended

to allow the CU to execute a specific response

routine.

Each interrupt is associated with an interrupt vec-

tor that contains the memory address of the

related interrupt service routine. Each vector is

located in the Program Space (EPROM Memory)

at a fixed address (see Interrupt Vectors Figure

4.2).

4.1 Interrupt Operation

If there are pending interrupts at the end of an

arithmetic or logic instruction, the one with the

highest priority is passed. Passing an interrupt

means to store the arithmetic flags and the current

PC in the stack and execute the associated Inter-

rupt routine, whose address is located in three

bytes of the EPROM memory location between

address 3 and 20.

The Interrupt routine is performed as a normal

code checking, at the end of each instruction, if a

higher priority interrupt has to be passed. An Inter-

rupt request with the higher priority stops the

lower priority Interrupt. The Program Counter and

the arithmetic flags are stored in the stack.

With the instruction RETI (Return from Interrupt)

the arithmetic flags and Program Counter (PC) are

restored from the top of the stack, which was pre-

viously described in Section 2.2.1.

An Interrupt request cannot stop fuzzy rule pro-

cessing, but this is passed only after the end of a

fuzzy rule or at the end of a logic, or arithmetic

instruction.

REMARK:

A fuzzy routine can be interrupted only

in the Main program. When a Fuzzy function is

running inside another interrupt routine an inter-

rupt request can cause side effects in the Control

Unit. For this reason, in order to use a Fuzzy func-

tion inside an interrupt routine, the user MUST

include the Fuzzy function between an UDGI

(MDGI) instruction and and UEGI (MEGI) instruc-

tion (see the following paragraphs), in order to dis-

able the interrupt request during the execution of

the fuzzy function.

Figure 4.1 Interrupt Flow

Figure 4.2 Interrupt Vectors Mapping

Figure 4.3 Global Interrupt Request Generation

INT_AC

INT_TRIAC/R

INTERRUPT

VECTORS

INT_TRIAC/F

INT_TIMER/PWM

INT_EXT

INT_TRIAC/P

RESET

NORMAL

PROGRAM

FLOW

INTERRUPT

SERVICE

ROUTINE

RETI

INSTRUCTION

INTERRUPT

Global Interrupt

Pending

User Global

Interrupt Mask

Macro Global

Global Interrupt

Request

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