MSPM0G3507: Question about Message RAM Configuration in MCAN

Frank(EP) Liu

Expert 4375 points

Part Number: MSPM0G3507
Other Parts Discussed in Thread: SYSCONFIG

Hi Expert,

I try to understand Message RAM Configuration in MCAN. Also, try to understand the setting from example code.

please help clarify few questions below.

from example, mcan_message_rx_tcan114x_LP_MSPM0G3507_nortos_ticlang

1. why TX buffer start address is 148? Filter starts from 0 and filter needs memory from 0-147?

2. follow previous question. Why i increase 1 "Number of Dedicated Transmit Buffers", end address increases 6( 6 32bit)? But the element size is 64 bytes.

3. Same question as above. If I increase\ decrease 1 from Number of RX FIFO0 Elements, End Address will increase\ decrease. but But the element size is 8 byte data field(2 32bits). As I know, it should be 2(R0+R1)+2(data field)=4,right?

4. from the code, start address is divided by 4. From TRM, it should be 32bits address. Why?

HW_WR_FIELD32(&mcan->MCANSS.MCAN.MCAN_RXF0C, MCAN_RXF0C_F0SA,
(msgRAMConfigParams->rxFIFO0startAddr >> 2U));

BR,

frank

7 months ago

0 Cash Hao11 7 months ago

TI__Mastermind 34145 points

Hi,

Frank(EP) Liu said:
1. why TX buffer start address is 148? Filter starts from 0 and filter needs memory from 0-147?

The standard filter takes 4 address and extended filter takes 8 address. It is just a demo to use 148 for the TX buffer here. You can modified it.

Frank(EP) Liu said:
2. follow previous question. Why i increase 1 "Number of Dedicated Transmit Buffers", end address increases 6( 6 32bit)? But the element size is 64 bytes.

I do not think this end address is related to the element size. Please check 20.4.19.1 Message RAM Configuration in TRM for more details. Same for question 3 and 4.

https://www.ti.com/lit/ug/slau846a/slau846a.pdf

Best regards,

Cash Hao

0 Frank(EP) Liu 7 months ago in reply to Cash Hao11

TI__Expert 4375 points

Cash,

for 1, you mean that I can set TX MSG RAM address to 8 due to filter only use 2*4 = 8.

for 2, from trm, address increases with each section. So, end address should be relative element size, right?

BR,

frank

0 Cash Hao11 7 months ago in reply to Frank(EP) Liu

TI__Mastermind 34145 points

Hi,

For 1, Yes, you can do that. For current version sysconfig, the information shows on the Sysconfig of the filter end address is not correct. This will be fixed in the coming version.

For 2, I look into how does the end address get calculate.

txBufEndAddr = txStartAddr + (txBufNum+txFIFOSize)*6;

In the equation, Number of Dedicated Transmit Buffers is txBufNum, and No of TX FIFO Elements is txFIFOSize. It is not relative to element size.

Best regards,

Cash Hao

0 Frank(EP) Liu 7 months ago in reply to Cash Hao11

TI__Expert 4375 points

cash,

Can you show me where I can find the equation below and 6 stands for?

txBufEndAddr = txStartAddr + (txBufNum+txFIFOSize)*6;

BR,

Frank

0 Cash Hao11 7 months ago in reply to Frank(EP) Liu

TI__Mastermind 34145 points

You can find it in <MSPM0_SDK>/source/ti/driverlib/.meta/MCAN.js.

Best regards,

Cash Hao

0 Frank(EP) Liu 7 months ago in reply to Cash Hao11

TI__Expert 4375 points

Cash,

Can you explain why it's 6

txBufEndAddr = txStartAddr + (txBufNum+txFIFOSize)*6;

BR,

frank

0 Cash Hao11 7 months ago in reply to Frank(EP) Liu

TI__Mastermind 34145 points

Hi Frank,

I do not know why it is 6. However, I do not think you need to concern about how it gets calculated. You just need to avoid overlapping the address based on the end address result given by the sysconfig.

Best regards,

Cash Hao

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MSPM0G3507: Question about Message RAM Configuration in MCAN