I am using the sn65hvd1050 CAN transreceiver for CAN interface . When I give the logic high to strobe pin(8) of transreceiver it not work in standby mode & i am not getting any receive interrupt, so please tel me how i can use the trans receiver in stand by mode to reduce the power consumption...my CAN speed is 1mbps ,
Pin 8 (S Pin) of the SN65HVD1050-Q1 is used to select the mode of the device. When the pin is low, the part is in Normal Mode. Does this mode work for your set up? When the S pin is high, the part enters Silent Mode, not Standby Mode. If you are looking for a Standby Mode (where a dominant state for greater than 5ms is passed to RXD for the micro to re-enable the device), the SN65HVD1050-Q1does not offer that feature. The low power mode that the SN65HVD1050-Q1 offers is Silent Mode. If you are looking for Standby Mode we offer a number of devices that have this feature including the SN65HVDA1040A-Q1, the SN65HVDA540-Q1 and the SN65HVDA541-Q1.
For Silent Mode the SN65HVD1050-Q1 the driver is disabled and the receiver remains fully functional. Therefore you will not be able to transmit any information to the bus but you should be receiving everything on the RXD pin (low in dominant state, high in recessive state).
Could you further describe what you mean by "I am not getting any receive interrupt"? Does the part work in Normal Mode but not Silent Mode? Could you share the schematic of how you are using the device?
yes you are right pin 8 is used for the mode selection . normal mode works properly for my setup . actually when i connect only two device on can bus one in normal mode & other in silent mode then silent mode device not receive any thing,but when i connect another device with normal mode all the device on bus work properly, please fin attched pdf file1321.default.pdf
There is a TI Applications Note that I think could help you with your issue that can be found here:
In your schematic do you have both terminations populated? As in, are R7, R8 and R9 all populated? This could cause an issue. Also how do you have the network set up for both the two transceivers and three transceivers configuration? If you are going to use the split pin it should be in the following fashion:
Where the resitors and cap create a low pass filter with -3dB point calculated with the equation above (R = 60Ω || 60Ω = 30Ω) . If your bus speed is 1MBPS then the CL value is 4.7nF.
In your schematic if you populated all three resistors, this could cause signal integrity issues and possible reflections on the bus. The nominal load that the transceivers is set up to see is 60Ω (120Ω at each end of the line in parallel). Each device is current limited and as the load impedance gets lower and lower eventually you will not get the differential voltage out.
If you have 2 nodes then two terminations would be correct, with each termination consisting of either the two sixty ohm resisters and cap (split termination) or one 120Ω resistor (standard termination). When you add the third node, no termination is needed.
Let me know if this helps.
thanks for reply .In our schematic we only populate the R7 & R8 .Please see the attached PDF file of schematic for our setup ,this setup work properly in normal mode but , when i switch the CAN NODE 2 &CAN NODE 3 from normal to silent mode ,the CAN NODE 2 &CAN NODE 3 not receive any think that sent by CAN NODE 1 & CAN NODE1 give me the transmit error. So tel me what is the exact issue..5545.default.pdf
I believe that you are having a system level failure.
In CAN each frame has an "Acknowledgement Field" which serves as a confirmation that a successful checksum (CRC) was done by the receiving nodes on the network. Therefore the transmitting node will send the Data Field and then will place the bus in the recessive state and "listen" for a dominant bit on the bus saying that the message that it sent was received and was in compliance with the defined standard. If the transmitting node does not get acknowledged (ACK) by any nodes on the network then it will post an error to the bus.
I believe that since all the nodes but one (which is the one that is transmitting, and is therefore not allowed to ACK its own message) on the network are in silent mode the transmitting node is not receiving the ACK bit which it is expecting and that it needs to verify its message is compliant. Therefore you have a transmit error from the sending node before the frame is even finished and that could also be why your other nodes do not receive a valid message either. After the Acknowledgement Field there is also an End of Frame Field which is required for all fields which is 7 recessive back to back bits. The transmitting node will send an error before this portion of the frame since it is not ACKed. Try putting one node in silent and two in normal mode and see if message transmission works.
Let me know if this works for you,
Thanks for reply . I all ready done what you suggest that , to putting one node in silent and two in normal mode & i found that the system was work properly.
So it means i can not put one device in normal mode & all other in silent mode on CAN bus ,so this is limitation of CAN driver or CAN system protocol ? , & also tel me how i can reduce the power consumption on CAN bus..?
It is a system protocol "issue". To further explain, all CAN messages which are also called frames in the ISO11898 protocol are made up of fields. Two fields that makes up all of these frames is the Cyclical Recovery Checking (CRC) field followed by the Acknowledgement Field (which states that the CRC that was just done for the data field just received either did or did not follow protocol). The device is part of the physical layer of the standard and no matter which device you pick, there will always need to be at least two devices communicating at one time.
In regards to your question about reducing overall power consumption on the bus, the only mode that has lower power consumption than Silent Mode is Standby Mode. Standby Mode will have power consumption in the low micro-amps range as opposed to the low milli-amps range for Silent Mode. Standby Mode offers by far the lowest power consumption and devices can be woken up remotely (i.e. over the bus) or locally from the mode pin (STB). But when a device is placed into this mode it will not receive any messages besides a wake-up request from the bus.
Thanks for reply , i will modify the setup according to system requirement,my another question is can we use the CAN bus without CAN transceiver on board level?
I am sorry but I do no understand what you mean by "Can we use CAN bus without CAN transceiver on board level?"
In short it mean can we use the CAN bus without CAN driver? because in our setup distance between two CAN node is less than 1feet & both the CAN nodes on same PCB..
I have never seen this done before. It would really help if you could elaborate more on your responses, it could help reduce the number of back and forth messages we are sending.
Are you are saying you want to take the twisted pair CAN bus directly to the board with no CAN devices? For that case I believe it would entirely depend on the micro you are using. What are you using?
Let me know,
I am using freescale automotive micro controller , also see the attached block diagram...3718.default.pdf
please find the attached file & tel me it is possible or not? 4621.default.pdf
The TX and RX signals that you showed are not the "CAN bus", only the CAN transceivers and physical twisted pair make up the PHY (physical layer) for the standard.
If you are going to have an actual CAN bus that interfaces with the board that you just showed me (a twisted pair of differential wires with recessive state of 2.5 volts), you will need a transceiver that can convert the differential bus signal to standard IO logic levels for the micro controllers and back for two way communication. If this is the only board, and the entire network then this different.
If the entire network that you are looking to implement is the block diagram above with no other nodes to communicate with and you are using two Freescale micro controllers that need to talk between each other I am not able to help you. I cannot give applications support for products that are not TI. You will have to work with Freescale directly.
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