topic Re: Interrupt while Flash write (HCS08 family) in 8-bit Microcontrollers

Interrupt while Flash write (HCS08 family)

prasad1 — Mon, 07 Aug 2017 09:34:39 GMT

Hi,

I am developing code for MC9SG8S08 microcontroller from HCS08 family. I have developed flash routine for burst programming as per reference manual of microcontroller.

While flash burst write is going on and any timer/SPI interrupt request received by CPU, will it generate any error? will be flash write happen successfully? What should be taken care in this scenario.?

The flash region where flash write is going to happen contains no data which will used by ISR.

Thanks in advance.

Re: Interrupt while Flash write (HCS08 family)

kef2 — Mon, 07 Aug 2017 13:03:37 GMT

S08 flash is not readable while it is being programmed. This means you not only have to move part of your flash erase/program code to RAM, but also have to disable interrupts for duration of program/erase operation. You could move some ISRs to RAM, but it's not possible to move interrupt vectors table to RAM.

Regards

Edward

Re: Interrupt while Flash write (HCS08 family)

prasad1 — Mon, 07 Aug 2017 14:27:02 GMT

Hi Edward,

Thanks for quick reply. flash program/erase region neither contains ISR code nor the DATA used by ISR. So is it ok to keep Interrupts on? I am using that flash to store some data only.

Thanks and Regards,

Prasad S Udawant

Re: Interrupt while Flash write (HCS08 family)

kef2 — Mon, 07 Aug 2017 14:34:41 GMT

No, it‘s not OK. As I said, interrupt vectors table must be readable, and while programming it‘s not readable. If you start programming and some interrupt is triggered, CPU will read wrong address of ISR and jump into the weeds. Interrupts must be disabled.

Regards,

Edward

Re: Interrupt while Flash write (HCS08 family)

prasad1 — Tue, 08 Aug 2017 05:50:03 GMT

Hi,

Thanks one again.But I still need some clarification.

I am going to write only some bytes of one flash page. Interrupt vector table is located on other flash page. In this scenario also while programming/erasing flash interrupt vectors table will not be readable?

Thanks in advance.

Thanks and regards,

Prasad S Udawant.

Re: Interrupt while Flash write (HCS08 family)

kef2 — Tue, 08 Aug 2017 06:25:24 GMT

Whole flash array/bank gets unreadable while being programmed/erased, not just page you erase program, whole array of pages. Small devices like SG8 have only single flash array. (Some big devices may have 2 big flash arrays. In such devices you could write/erase one array/bank while reading or executing code from another bank.)

Edward