what is the purpose of the mailbox id?

[buccno]

If the mailbox ID's purpose, for example 

set the nth mailbox,  When I increase the ID value, for example, if I double it, does the mailbox covers double?

[buccno]

For example, I define a macro in my code, #define TX_MAILBOX_IDX 1 -> that means selected address offset?

If that is true, my address offset is 0090? or 0090 - 0080? 
so, 

I ask this because, in my code sample, I was changing the message buffer index value(RX or TX, RX and TX) anything changed. I use an 8-byte payload.

[Senlent]

Hi@buccno

I didn't understand your question. If you have questions about the details of FlexCAN, you can read our data sheet, and we also have a complete demo for customer reference,

for example:

https://community.nxp.com/t5/S32K-Knowledge-Base/S32K1xx-FlexCAN-Mask-Setting-Demo/ta-p/1519753 

https://community.nxp.com/t5/S32K-Knowledge-Base/S32K-Examples/ta-p/1108990 

[Senlent · Accepted solution]

Hi@buccno

please take a look at the S32K-RM rev13

[buccno]

Actually, I cannot understand, If I increase the mailbox index, does my message buffer's memory area increase?