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Tilecal Read-Out Driver


This page contains the information regarding hardware, firmware and software designs for the ROD development at Valencia. Latest documentation and code are provided for this purpose.

General overview

The Read Out Driver (ROD) is the intermediate link of the chain between the front-end electronics and the general data acquisition system of the ATLAS detector (TDAQ), see Figure 1. It represents the backend electronics of the Hadronic Tile Calorimeter.

The Tilecal ROD has to read and process data from 9856 channels each 10µs and it must be able to work in real time. The data gathered from these channels are digitized and transmitted to RODs with high-speed optical links. There are 256 digital optical links (1 per FEB electronics drawer) that the ROD should be able to manage and process at Level 1 trigger rate (100 kHz) and send to the Read Out System (ROS) which is the next step in the ATLAS DAQ chain. At this stage a second trigger decision (Level 2 trigger ~1 kHz) will allow data to go to next step using algorithms based in Regions of Interest (ROI). Data passing the Level 3 trigger (~100Hz) will finally be stored in tapes for offline analysis. See the numbers in Table 1.

Figure 1: Tilecal Detector partitions and readout

Number of Channels
Number of input links (optical fiber)
Number of channels per drawer (EB)
Number of channels per drawer (CB)
Input event size per FEB (7 samples)
0,43 Kbytes
Input Data Bandwidth @ 100kHz Lvl1 ATLAS rate
14,03 Gbytes/sec
Number of Drawers (FEB) per ROD module
Number of RODs
Number of Read Our Links (ROL ROD ROB mapping 4:1)
Output Data Bandwidth @ 100kHz Lvl1 ATLAS rate
6,70 Gbytes/sec
Typical output event size per ROD link (4 to 1 I/O mapping)
1,10 Kbytes
Total processing power needed
68992 MIPs

Table 1: RoD facts

Summary of ROD basic functionalities:

  1. ROD Organization: The ROD modules are VME 9U modules controlled by a rod controller (VME SBC computer) plus other trigger modules (TBM) mounted in a 9U VME ROD Crate.
  2. DATA PROCESSING: Raw Data gathering from first level de-randomizers at the L1A event rate 100 kHz. To provide energy, timing and pile up estimation (chi2) to the next level by optimal filtering. Keep the possibly to pass raw data without processing when it be advisable (pile-up, high energy events).
  3. TRIGGER: TTC signals will be present (latency ~2us after L1A) at each module providing ROD L1ID, ROD BCID and Ttype (trigger type).
  4. ERROR DETECTION: These are synchronism Trigger Tasks. The ROD must check that the owner BCID and L1ID numbers match with the ones received from the FE. If a mismatch is detected, an error flag must be set with some error code.
  5. DATA LINKS: Event data must be sent to ROB through the standard ATLAS readout links and standard DAQ-1 data format at the L1A event rate (100 kHz).
  6. BUSY GENERATION: Provide a ROD busy signal in order to stop L1A generation. A global OR of the RODs busy per sub-detector has to be provided to the CTP.
  7. LOCAL MONITORING: VME access of the data during a run without introducing dead-time or additional latency in the main DAQ data. Each ROD motherboard is VME slaves commanded by the ROD Controller (VME SBC).


Last updated 20-Apr-2005

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Created and Maintained by Juan Valls & Jose Castelo © IFIC, Universitat de València

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