Forum Discussion
ContributorElectrical IDLE entry & exit detection on receiver side of the transceiver
Hi,
I am working on Arria 10 Transceiver for a custom protocol and I need to put the transmitter in electrical IDLE as per the protocol.
On the transmitter side, I can put transmitter in electrical IDLE using tx_pma_elecidle port.
On the receiver side, I need to detect the electrical IDLE. I am thinking to use CDR status status "lock to data & lock to ref" ports.
I understand that whenever transmitter is active both lock to data & lock to ref are asserted (1). Whenever the transmitter goes into electrical IDLE, the lock to data status in the corresponding receiver in the other side goes low (de-asserted) and receiver will continue to lock to ref only. Whenever the linked transmitter exits electrical IDLE, the CDR status of the receiver (lock to data) asserted again.
In this way I am planning to detect the electrical IDLE entry & exit in the receiver side. Please clarify whether my understanding is correct or not.
With regards,
HPB
10 Replies
CheepinC_alteraRegular Contributor
Hi HPB,
As I understand it, you have some inquiries related to using RX CDR LTD status to detect when the TX is being put into electrical idle. For your information, the CDR might take some time before it lose lock to data and de-assert the LTD. I would like to recommend you to explore into using the rx_std_signaldetect signal to detect the TX electrical idle. Whenever the TX is in elecidle, there should be no valid signal arrive at the RX. The RX signal detect will de-assert. Note that you would need to configure the signal detect threshold to the right settings to ensure normal operation of your link.
For your reference, as per the A10 user guide, in SATA application, the following values are used:
For SR: sd_threshold for SATA = SDLV_4
For LR: sd_threshold for SATA = SDLV_6
Also, you would need to have 8b10b block enabled when you are using this signal detect.
Please let me know if there is any concern. Thank you.
Best regards,
Chee Pin
HBhat2Hi @cheepinc_Intel ,
Thanks for the response & options.
rx_std_signaldetect : This port is accessible when I select PCIe configuration. In my development, I am using Basic (Enhanced PCS) mode as I am writing my own custom PCS for the protocol. So, I think rx_std_signaldetect may not be useful for me.
One more thing, whether is it possible to use rx_data_valid port for the same purpose (to know whether the connected TX is in electrical IDLE or not) ?
With Regards,
HPB
- CheepinC_altera
Hi HPB,
Thanks for your update. As I understand it, you are using Enhanced PCS and thus the rx signal detect feature is not available. In this case, you may use the CDR lock-to-data status to tell if the TX has gone into electrical idle state. Additional info to share is that the CDR lock-to-data status will toggle when there is no valid data. Only when the assertion remain high for more than 4us would indicate the CDR has achieve LTD.
Regarding the RX data valid signal from the FIFO, this is part of the FIFO which is after the CDR. Thus, I think using CDR lock status would be more appropriate.
Please let me know if there is any concern. Thank you.
Best regards,
Chee Pin
- HBhat2
Hi,
"
I understand that whenever transmitter is active both lock to data & lock to ref are asserted (1). Whenever the transmitter goes into electrical IDLE, the lock to data status in the corresponding receiver in the other side goes low (de-asserted) and receiver will continue to lock to ref only. Whenever the linked transmitter exits electrical IDLE, the CDR status of the receiver (lock to data) asserted again.
"
That means above understanding is correct & based on lock to data de-assertion & assertion, I can arrive at the conclusion that corresponding TX is in IDLE or not. [Apart from some delay to assert & de-assert the status]
With regards,
HPB
- CheepinC_alteraHi HPB, Just would like to further clarify on the behavior lock-to-data and lock-to-ref signals: "I understand that whenever transmitter is active both lock to data & lock to ref are asserted (1)." [CP] When transmitter is active and valid data present at the RX, the CDR will achieve LTD mode. The lock-to-data signal will be High. The lock-to-ref signal can be ignored (it may stay at High or toggling) "Whenever the transmitter goes into electrical IDLE, the lock to data status in the corresponding receiver in the other side goes low (de-asserted) and receiver will continue to lock to ref only." [CP] When there is no valid data present at the RX, the lock-to-data and lock-to-ref signals will be toggling. Please let me know if there is any concern. Thank you. Best regards, Chee Pin
- CheepinC_altera
Hi,
I believe the initial inquiry has been addressed. This thread will be transitioned to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.
