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One major feature of the GBCR is the retime mode which is using a similar design as in lpGBT, but GBCR has a finer DLL delay granularity of 50ps per step vs 100ps in lpGBT. This is an essential utility to allow optimized control of the signal sampling time as the expected good time window at full chain loss is narrow. The control setting for this mode:
| Register | Value | Comments |
|---|---|---|
| dllEnable | True | Enable DLL clock for for retiming |
| dllCapReset | False | |
| dllForceDown | False | DLL can have harmonic lock problem which would need dllForceDown=T to release it |
| dllChargePumpCurrent | 0x0 | Set charge injection current to min value. Higher current enables faster locking but may cause larger jitter. |
| dllClockDelay | scan | Scan this delay for the active channel for good BER window bathtub. |
Some Useful Links
- Optoboard System Documentation
- FELIX JIRA (Oct/22) on optoboard + ITkPix readout setup
- CERN mattermost Bern-Optoboard channel
- Talk (Dec/9/2022) by Angira Rastogi on Optoboard-FELIX setup at LBNL
GBCR Documentations