09/01/2016james leaver slink current progress. 09/01/2016james leaver hardware setup slink receiver...

22/04/23 James Leaver

SLINKCurrent Progress


Hardware Setup

Slink Receiver

Generic PCI Card

Slink Transmitter

Transition Card (ECAL)

VM

E B

ackp

lane

FED Controller

Slink Controller

Control via VXI-MXI-2

LVDS Cable

FED


Slink Verification

• Configure FED to send test patterns:– Simple counter– Alternate lines of all

As and all 5s

• Drive FED with software triggers:– Throttle triggers using

software ‘waits’ and by setting QDR buffer occupancy thresholds

• Simply receives all data sent from FED

• Compares received data with current expected test pattern

FED PC SLINK PC


GreenGreen: Slink CLK

YellowYellow: Write Enable

BlueBlue: Bit 0 of Data Stream

PinkPink: Bit 1 of Data Stream

Example Data TransmissionTest Pattern: Alternate lines of As and 5s, Scope Length: 10

Measured from Transition Card






A Bad Clock?Test Pattern: Alternate lines of As and 5s, Scope Length: 10

Measured from Transition Card, Persistent Display






Clock Signal at the FED

Measured on the FED; Slink Connected






Clock Signal at the FED

Measured on the FED; Transition Card Disconnected


Spice Model of Clock Path


Spice Model Results

BlueBlue: CLK at FED VME connector

RedRed: CLK at output connector on Transition Card

YellowYellow: CLK at input to Transmitter FPGA


The Only Way to Remove Reflections…?


The Only Way to Remove Reflections…?

CLK is good at all locations – but impractical hardware solution


Clock at Input to Transmitter FPGA

The Slink clock is clean where it matters, as Spice model predicts


Slink Error Rates

• Have sent 18.3 Gbytes of data from FED to Slink Receiver

– Used alternate lines of all As and all 5s; highest possible switching rate

• No errors observed in transmitted data

Probability that a word will be transmitted incorrectly via Slink is:

1.22 x 101.22 x 10-9-9 @ 95% CL @ 95% CL


Required Data Rates

• To guarantee (95% CL) that no more than 1 word will be sent incorrectly per month of normal LHC operation, need to transmit words (without errors)

• At current maximum data rate, would take ~16 years!

• Need to find a way to increase data rate:

– Could potentially output ~600 Mbytes/sec from the FED (reducing validation time to ~30 days)

141004.2


FED Behaviour at High Data Rates

• With a fixed wait of > 60.07ms between software triggers:

– QDR buffer always empty when next trigger arrives

– FED operates normally

• With a fixed wait of < 60.07ms between software triggers:

– QDR buffer rapidly fills to current limit (1→ 10 frames)

– FED operates normally for some period of time

– FED randomly stops sending data

An Extreme Example

Test Pattern: Alternate lines of all As and all 5s, Scope Length: 1020


Why Does the FED Stop?

• Backpressure from the Slink?

– At high trigger rates, backpressure is exerted multiple times during period in which FED is working

• Overflow of QDR Buffer?

– FED stops working even with a QDR buffer limit of 1 frame

• Overflow of Front End Buffer?

– Backend Status Register would indicate not…

– But getChannelBufferOccupancy() function in ‘Fed9U’ software returns dubious values

– Seems most likely cause


Data Rate Challenges

• Need to prevent FED lock-ups

• Software triggers insufficient

– Limited to a maximum of ~100 Hz

– Need to use hardware triggers - generated with FED Tester?

• Need to increase efficiency with which Slink PC manages received data

– Currently have to run Slink software in ‘debug’ mode (raw data access) due to mismatch between output FED header/trailer words and format required for automatic event handling


Conclusion

• Data can be read from the FED via Slink

• No errors yet observed

• Nothing to suggest that FED hardware requires modification

• Firmware/Data Rate issues to be resolved…

09/01/2016james leaver slink current progress. 09/01/2016james leaver hardware setup slink receiver...

Documents

fed tester

sdrive fed

slink software

data streammeasured

gbytes of data

data streampink

fed vme connectorred

high data rateswith