EM78P159NP datasheet(29/48 Pages) EMC

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EM78P159N

8-Bit Microcontroller with OTP ROM

Product Specification (V1.0) 03.10.2006

• 25

(This specification is subject to change without further notice)

4.6 Interrupt

The EM78P159N has three falling-edge interrupts as listed herewith:

1) TCC overflow interrupt

2) Port 6 Input Status Change Interrupt

3) External interrupt [(P60, /INT) pin].

Before the Port 6 Input Status Change Interrupt is enabled, reading Port 6 (e.g., "MOV

R6,R6") is necessary. Each Port 6 pin will have this feature if its status changes. Any

pin configured as output or P60 pin configured as /INT is excluded from this function.

The Port 6 Input Status Changed Interrupt can wake up the EM78P159N from Sleep

mode if Port 6 is enabled prior to going into the Sleep mode by executing SLEP. When

the chip wakes-up, the controller will continue to execute the succeeding address if the

global interrupt is disabled or it will branch into the interrupt vector 008H if the global

interrupt is enabled.

RF is the interrupt status register that records the interrupt requests in the relative

flags/bits. IOCF is an interrupt mask register. The global interrupt is enabled by the

ENI instruction and is disabled by the DISI instruction. When one of the interrupts

(enabled) occurs, the next instruction will be fetched from address 008H. Once in the

interrupt service routine, the source of an interrupt can be determined by polling the flag

bits in RF. The interrupt flag bit must be cleared by instructions before leaving the

interrupt service routine and before interrupts are enabled to avoid recursive interrupts.

The flag (except ICIF bit) in the Interrupt Status Register (RF) is set regardless of the

status of its mask bit or the execution of ENI. Note that the outcome of RF will be the

logic AND of RF and IOCF (refer to figure below). The RETI instruction ends the

interrupt routine and enables the global interrupt (the execution of ENI).

When an interrupt is generated by the INT instruction (enabled), the next instruction will

be fetched from Address 001H.

IN T

EN I /D I S I

IO D

RF W R

I O CF RD

IO C F W R

IR Q n

IR Q m

RFR D

IO C F

/R E S E T

/I R Q n

VC C

CL K

Figure 4-7 Interrupt Input Circuit

EM78P159NP Datasheet(PDF) 29 Page - ELAN Microelectronics Corp

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