topic Re: K22 Flexbus in Kinetis Microcontrollers

K22 Flexbus

adamkiburz — Wed, 22 Jul 2015 19:08:37 GMT

I am designing with the K22FX512AVLQ12 in mind. I have a memory interface I put together based on what I understood of the FLEXBUS in the K22P144M120SFV2RM.pdf reference manual. However I have seen several comments in Freescales community boards about problems people are having using a x16 bit data bus. AN4393 doesn't talk about using a non-multiplexed interface for a x16 bit data bus. So, before I make a board, I wanted someone to advise me that this design will work, and if there are other limitations with it if it does. For example, can it read/write an odd or even byte without affecting the corresponding even or odd byte? Will a 32-bit aligned read or write actually result in two memory cycles to the SRAM? Will non-aligned reads and writes work? If the design does work, it should be added to AN4393.

Also, Table-4-1 of the reference manual shows the FLEXBUS to be in 5 different regions of the memory map. The comments I have seen recommend using the "External Peripheral" space. "write-back" and "write-through" suggests a cache, but there is no mention of a cache for the FLEXBUS in the reference manual.

Re: K22 Flexbus

Hui_Ma — Thu, 23 Jul 2015 03:18:02 GMT

Hi Adam,

There should without problem for customer to use 16-bit data port with non-multiplexed mode.

When using the non-multiplexed mode, customer need to make sure the Flexbus pin resource is enough for the application.

For using 16-bit data port, the FB_AD0 pin is obsoleted as address pin, it just read the data with 16 bits (2 bytes).

If there exists address non-aligned, there still could read data out, while it will take more cycles (time).

It could read the odd byte and even byte with byte enable signal.

Wish it helps.

Have a great day,
Ma Hui

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Re: K22 Flexbus

adamkiburz — Thu, 23 Jul 2015 14:17:34 GMT

Hi Ma,

Thank you very much for the quick response! I will let you know if I have more questions.

Thanks again.

Adam

Re: K22 Flexbus

michaelhuslig — Tue, 04 Aug 2015 20:02:54 GMT

Adam posted this question for me. Please refer to External SRAM and non-multiplexed Flexbus and comment.

Mike Huslig

Re: K22 Flexbus

adamkiburz — Tue, 04 Aug 2015 22:04:50 GMT

Hi Ma,

Can you please take a look at the attached schematic and let me know if your answer is still valid?

Thanks,

Adam

Re: K22 Flexbus

Hui_Ma — Wed, 05 Aug 2015 03:11:34 GMT

Yes, I think customer using FB_AD1 connects with SRAM's A0 is quite right.

Customer need to config Flexbus port size to 16-bit.

For the Kinetis Flexbus module is original from ColdFire product, I attached a ColdFire product MCF54451 Flexbus connects with NOR Flash (16-bit data port) for your reference:

Have a great day,
Ma Hui