[SOLVED] can camunication using MCP2515 AND AT89S8252

[debabrta kar]

hi, i am working with can protocol using mcp2515 and at89s8252 as host controller....i read the documents ...i have a doubt on bus recovery....actualy after a node goes bus off how it recovers...it is written in dacumnets that for recovery 128*11 consecutive recessive bits will send ...i mean who will send these bit and who will recieve...i m really confused plz guide me thank you

 

[embpic]

U can't use only at89s8252 and mcp2515 directly u will need to use can Transceiver that is mcp2551 .

 

[debabrta kar]

yes sir i am using transceiver i.e pca82c250......

 

[embpic]

i think bus go to bus off state when there is maximum error in tx or rx so reconfigure your device and check the at position error is getting.
bus off state can be change only decreasing the error count of rx and tx.

 

[debabrta kar]

thank u for u sugeestion sir, actually i am asking that what will be the effect of bus after a node goes buss off due to transmit error count value goes above 255....who will send the 128*11 consecutive recessive bit plz help me here....

 

[Emb4U]

I think MCP2515 sends that 128*11 consecutive recessive bits because the MCP2515 handles the counter and counts the error upto 255. When the count goes to 256 it enters to bus off condition. Then MCP 2515 sends 128*11 recessive bits to recover from bus off condition.

 

[debabrta kar]

dear, embd4u, as per your answer i think mcp2515 handles the busoff condition and its not an overhead for mcu to reset the can controller . so we can say that mcp2515 is having self reset ..right..?..please suggest

 

[embpic]

yes all CAN controlling related action taken by CAN controller only.