BESIII electronic system consists of four main parts, Drift Chamber Electronics, Electromagnetic Calorimeter Electronics, Time Of Flight Electronics, Muon Counter Electronics. All the system is based on VME bus.

* Drift Chamber Electronics

The BESIII MDC (Main Drift Chamber) electronics system is designed to process the output signals from 6796 sense wires of MDC. The main tasks of the MDC electronics are the following:

• To measure the drift time of ionized electrons produced by charged particles towards anode wires (sense wires) to provide position information of particles passing through the chamber, so as to determine the momentum of charged particles. Time resolution better than 500ps.
• To measure the charge collected by anode wires (sense wire) to determine the energy loss of particles per unit length, dE/dx, so as to identify particles. Dynamic range from 15 f.C. to 1800 f.C
• To provide the hit information to the trigger system, which will be used as one of the level-1 trigger conditions.

 MDC 512 channel test system

* Electronmagnetic Calortimeter Electronics

The main purpose of electromagnetic calorimeter electronics is the charge measurement to determine the energy deposited in the CsI crystals.

The traditional charge measurement method adopted in the read out electronics is to integrate the output current from the detector. The voltage peak of the signal waveform, after amplification and shaping of the integrated signal, is proportional to the detector output charge, which can then be measured through the peak voltage.

 Electromagnetic calorimeter electronics adopts digital pipeline method to hold the data in compliance with the 6.4s level-1 trigger latency, so that no good events will be lost before the level-1 trigger comes. Data read out follows the VME bus standard.

The dynamic range is 15bits and the equivalent noise charge(energy) is 1000 electrons (200KeV).

       EMC 384 channel test system

*  TOF Electronics

The primary task of the TOF electronics is to measure the flight time of charged particles, referred as the “time measurement”. In order to correct the timing error caused by the “time-walk” effect, the total charge from scintillators should also be measured, referred as the “charge measurement”. Therefore the three essential functions of TOF electronics are as follows:

j Time measurement

k Charge measurement

l Fast timing signals for trigger.

The required time measure resolution is 25ps. We use HPTDC chip designed by CERN.

* Muon Counter Electronics

Muon counter (MC) is constructed with 9088 channels (4992 at the barrel and 4096 at the endcup) by Resistive Plate Chambers (RPCs). The tasks of the MC readout system are to transform the information from strips of the RPCs into digital data, handle the data of the event after trigger signal, store the data into the sub-event buffers with the relative header, and wait for calling by DAQ system.

The readout system of the MC contains one VME crate and four power supply crates. In the VME crate there is a readout module containing 40 data chains, each of which is composed of the 256-bit data from the strips of the RPC. The readout system is able to scan 10,240-bit data in parallel in order to satisfy the requirement of the MC.

In addition, the electronics system of the MC contains a test subsystem, which can test the whole readout system online.

 Muon FEE boards