1. Where does encoding exactly take place ??
It happens in PCS (Physical coding sub layer)
It happens in PCS (Physical coding sub layer)
2. Gen 3.0 -> does PCS exist ?? Why ??
Yes. Though 128/130b encoding does not take place in PCS for gen 3.0. Elastic buffer and after reset the first step, receiver detection is also responsibility of PCS.
Yes. Though 128/130b encoding does not take place in PCS for gen 3.0. Elastic buffer and after reset the first step, receiver detection is also responsibility of PCS.
3. Why 10 b encoding is used ??
To generate enough transition (DC- Balance) of 1 and 0. So receiver can recover the clock. Moreover, Continuous 1 will decay at the receiver and will be detected as 0.
To generate enough transition (DC- Balance) of 1 and 0. So receiver can recover the clock. Moreover, Continuous 1 will decay at the receiver and will be detected as 0.
4. Is scrambling used for just clock recovery and encryption ?? Why??
Scrambling is used for gen 3 is more effective and used to maintain DC Balance and transition density, over a long period of time. Moreover in Gen3 TS1 and TS2 are modified such that the maintain DC Balance.
Scrambling is used for gen 3 is more effective and used to maintain DC Balance and transition density, over a long period of time. Moreover in Gen3 TS1 and TS2 are modified such that the maintain DC Balance.
5. Use of overhead bits??
In Gen3 it is used to identify data or orderset.
In Gen3 it is used to identify data or orderset.
6. Why SDS and EDS ?? Is it an O.S. ??
SDS is an O.S. Because you need to inform every lane regarding starting of data stream. SDS is also used to
enter in Loked phase. While EDS is just end of data stream which is not required to place at every lane.
SDS is an O.S. Because you need to inform every lane regarding starting of data stream. SDS is also used to
enter in Loked phase. While EDS is just end of data stream which is not required to place at every lane.
7. Why is Scrambler always enabled in GEN 3.0 ??
Scrambling is used for gen 3 is more effective and used to maintain DC Balance and transition density, over a long period of time. Moreover in Gen3 TS1 and TS2 are modified such that the maintain DC Balance.
Scrambling is used for gen 3 is more effective and used to maintain DC Balance and transition density, over a long period of time. Moreover in Gen3 TS1 and TS2 are modified such that the maintain DC Balance.
8. How is Syncheader transmitted by SERDES ??
Serdes convert 128 bits of data in to 130 bit. This 2 bits are sync header.
- If PCI-Express Endpoint generate I/O or Configuration Request, Completion Status of Completion generated from Root Complex will be Unsupported Request
- When a device is in FC_INIT2 state (for any VC), it should accept and process TLPs. So that it can decode the VC (By TC-VC mapping) for that TLP and can set FC_INIT2 Flag.
- If a port receive different credit value in successive INITFC1 packet in FC_INIT1 state , It is not a protocol error.
- If a requester send CfgWr or IOWr with data poisoning , completion status of Cpl sent from completer is unsupported request.
- We can have a different TC-VC mapping for any physical function. VC Resource Register (For TC-VC Mapping) is different for each function.
- PCI-Express Extended Capability is required by each function of multi function device.
- Advanced Error Capability (Optional) is separate for each function.
- Device Serial number capability is optional feature may be implemented in a single function device. All multi-function devices that implements this optional capability must implement it for Function 0; other Functions are permitted to implement thiscapability and if implemented, must return the same Device Serial Number value as thatreported by Function 0.
- Power budgeting capability (Optional) is separate for each function.
- Root Complex generates the Memory Write and Memory read transactions which does not fall in the address range of any functions Memory space of Endpoint. All EP functions have AER capability.Received TLP in End Point will be treated as Unsupported Request.
- In a multi-Function device, PCI Express errors that are not related to any specific Function within the device, are logged in the corresponding status and logging registers of all Functions in thatdevice.
- On the detection of the Unsupported Request, a multi-Function device should generate at most one error reporting Message of a given severity, where the Message must report the Requester ID of a Function of the device that is enabled to report that specific type of error. If no Function is enabled to send a reporting Message, the device does not send a reporting Message. If all reporting-enabled Functions have the same severity level set for the error, only one error Message is sent. If all reporting-enabled Functions do not have the same severity level set for the error, one error Message for each severity level is sent.
- Endianness of config space is little endian and it is fixed.
