C166: RTC Interrupt Request Flag remains set in Simulator

Information in this article applies to:

• C166 All Versions

QUESTION

I'm using the ST10F269 Real-Time Clock (RTC). The manual states that an interrupt request flag is set by hardware whenever a service request from the respective source occurs. It is cleared automatically upon entry into the interrupt service routine or upon a PEC service.

However, this does not seem to be the case in the µVision simulator. Is there an error in the simulator?

ANSWER

No. There is no error in the Simulator.

The RTC is implemented as an X-Peripheral. RTC interrupts in the ST10F269 are connected indirectly to the Interrupt Controller as an alternate source for the external interrupts. Using EXISEL, you may select the source for the external Interrupt (Port2, an Alternate Source like the RTX, or Both combined through AND/OR).

Therefore, when an RTC interrupt occurs, it sets an External interrupt flag which is then automatically cleared upon entry into the interrupt service routine. The RTC flag which caused this interrupt is not cleared automatically. This is by design. If the External Interrupt is selected as RTC Interrupt OR'ed with Port2, you would be unable to distinguish which caused the interrupt if the RTC flag were to be cleared by the hardware.

MORE INFORMATION

• C166/ST10 Microcontroller User's Manuals

Last Reviewed: Thursday, February 25, 2021