|Front-End Electronics (FEE)|
|Last modified: 14:10 Friday 01-Oct-1999|
Each readout board has as many as nine sections. Each section is equipped with a Xilinx programmable logic chip, independent voltage regulators and a pair of connectors and cables, supporting up to four FEE cards. No more than 36 FEE cards connect to a single RDO.
FEE card pedestals and pedestal RMS are very sensitive to readout board grounding conditions. Lower impedance connections (i.e., grounding braid) to the sector tend to reduce RMS. A twisted-pair trigger cable supplies a bused 4-bit trigger word to each attached readout board. The connectors are unkeyed, relying on the user to align "Pin 1's" of the cable plug and RDO connector; on each, "Pin 1" is marked by a small triangle molded into the side of the connector. The RDO end of the cable must be terminated with (eight?) 100--120 ohm resistors. Inner and outer sectors are usually supplied with independent cables.
The following hex trigger words are defined for the readout boards in Trigger/Clock Distribution Tree, (Req. Doc., V1.2, February 29, 1996), by V. Lindenstruth et al.:
Slow controls can monitor a number of readout board parameters. This includes two thermocouples on leads that can plug into the RDO. The slow controls interface is attached through a flat, narrow ribbon cable. The RDO end of this cable must also be terminated with (six?) 100--120 ohm resistors. MiniDAQ per se can operate without these connections.
Each readout board is also equipped with a modem interface, and their address space can be accessed via this.
Separate floating magneto-resonance power supplies provide +/- 8 VDC to each RDO. The + and - current draws are similar, making the ground return current small. (On an early prototype with a lower quality power connector, the potential developed across a bad ground connection may be too low to clear the oxide layer.)
Data is sent to DAQ via a 50- or 62.5-um multi-mode fiber. This link is strictly one way.
Note: the RDO ID is loaded only as the RDO is powered up; changing the DIP-switch settings does not change the RDO ID until it is power-cycled. If the ID is not correct, the data will be corrupted, unanalyzed and/or incorrectly analyzed.