SPRAD59 October   2023 TMS320F280039

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Key Differences Between DCAN and MCAN
  6. 3 Module Initialization
    1. 3.1 DCAN Initialization
    2. 3.2 MCAN Initialization
    3. 3.3 Initialization sequence
    4. 3.4 Code Snippets for Module Initialization
  7. 4 Bit Timing Configuration
  8. 5 Message RAM Configuration
  9. 6 Interrupt handling
    1. 6.1 MCAN Interrupt Sources
    2. 6.2 DCAN Interrupt Handling
    3. 6.3 MCAN Interrupt Handling
  10. 7 Transmitting data
    1. 7.1 Basic Transmission Process
      1. 7.1.1 Transmission with DCAN
      2. 7.1.2 Transmission with MCAN
    2. 7.2 MCAN Vs DCAN Transmit Procedural Differences
    3. 7.3 MCAN Transmit Concepts
      1. 7.3.1 Tx Event FIFO
  11. 8 Receiving Data
    1. 8.1 Introduction to Reception
    2. 8.2 Basic Reception Process
      1. 8.2.1 DCAN Reception
      2. 8.2.2 MCAN Reception
    3. 8.3 Filter Elements
      1. 8.3.1 Filter Element Structure
    4. 8.4 Rx Buffer
      1. 8.4.1 Receiving in Rx Buffer
    5. 8.5 Rx FIFO
      1. 8.5.1 Receiving in Rx FIFO
    6. 8.6 Receiving High Priority Messages
  12. 9 Avoiding network errors
  13. 10References

8.3.1 Filter Element Structure

Standard (or Extended) Filter Elements are defined by the following fields:

  • sft (or eft) determines what kind of filter is to be implemented.
  • sfec (or efec) determines where the accepted frame is to be stored or if the frame is to be rejected.
  • sfid1 and sfid2 (or efid1 and efid2) determine which message IDs are matching.

The individual functions can vary based on the filter type as shown in Table 8-1 and Table 8-2:

Table 8-1 Standard Filter Element Parameters
Parameter Description
Standard Filter Type (SFT) 0x0 : Range Filter from SFID1 to SFID2 (SFID1<= SFID2)
0x1 : Dual ID Filter for SFID1 or SFID2
0x2 : Classic Filter: SFID1 = Filter; SFID2 = Mask
0x3 : Filter Element Disabled
Standard Filter Element Configuration (SFEC) 0x0 : Disable Filter Element
0x1 : Store in Rx FIFO 0, if filter matches
0x2 : Store in Rx FIFO 1, if filter matches
0x3 : Reject ID, if filter matches
0x4 : Set Priority, if filter matches
0x5 : Set Priority and store in Rx FIFO 0, if filter matches
0x6 : Set Priority and store in Rx FIFO 1, if filter matches
0x7 : Store in Rx Buffer, ignore SFT [1:0] field
Table 8-2 Extended Filter Element Parameters
Parameter Description
Extended Filter Type (EFT) 0x0 : Range Filter from EFID1 to EFID2 (EFID1<= EFID2)
0x1 : Dual ID Filter for EFID1 or EFID2
0x2 : Classic Filter: EFID1 = Filter; EFID2 = Mask
0x3 : Range Filter from EFID1 to EFID2 (EFID1<= EFID2), XIDAM mask not applied
Extended Filter Element Configuration (EFEC) 0x0 : Disable Filter Element
0x1 : Store in Rx FIFO 0, if filter matches
0x2 : Store in Rx FIFO 1, if filter matches
0x3 : Reject ID, if filter matches
0x4 : Set Priority, if filter matches
0x5 : Set Priority and store in Rx FIFO 0, if filter matches
0x6 : Set Priority and store in Rx FIFO 1, if filter matches
0x7 : Store in Rx Buffer, ignore EFT field

An example for setting up Standard Filter Elements is shown below:

If the application requires filter configuration such that

  • Frame with Message ID = 0x04 must be stored in Rx Buffer Element 5 (buffer element range is from 0 to 63)
  • Frame with Message IDs 0x371, 0x375, 0x379, 0x37D must be stored in Rx FIFO 0
  • Frame with Message IDs 0xF4 and 0x23 must be rejected
  • Frame with Message IDs in the range [0x734 to 0x75A] must be stored in Rx FIFO 1

In that case, the Standard Filter Elements to be added is shown in Table 8-3 :

Table 8-3 Standard Filter Element Configuration
Filter Element Number
(filtNum)		 Standard Filter Type
(sft)		 Standard Filter Element Configuration
(sfec)		 Standard Filter ID 1
(sfid1)		 Standard Filter ID 2
(sfid2)
0 xx = Don't care 111 = Store in Rx Buffer 0x04 0x05
1 10 = Classic Bit Mask Filter 001 = Store in Rx FIFO 0 0x371 (filter) 0x0C (mask)
2 01 = Dual ID 011 = Reject 0xF4 0x23
3 00 = Range Filter 010 = Store in Rx FIFO 1 0x734 0x75A

When accessing any Standard Filter Element, the address is the starting address initialized to the register (MCAN_SIDFC.FLSSA) during Message RAM configuration plus the word size of the filter element times the index of the filter element. However, while evaluating any received frame against the filter list, the module only checks filters up to the number initialized to the register (MCAN_SIDFC.LSS) during Message RAM Configuration.

Note: Ensure that the Filter Element index does not exceed the initialized value (MCAN_SIDFC.LSS); otherwise the filter element reference can malfunction.

GUID-20231010-SS0I-WQJB-RHKH-V88DG23SJFHG-low.png Figure 8-2 MCAN Filter Configuration