Front-End Crates
DAQ III Overview
Data-Links
CLEO III Data-Mover
Once data read-out and conversion are complete a data-board releases its
Board_Busy line.
When the Trigger Interface Module senses that the last data-board in this crate is done
it informs the CLEO III Trigger/Data-Flow control system to re-enable the experiment. In
parallel an interrupt signal is asserted. The Data-Mover CPU module reacts to this
interrupt and a DMA engine on the Data-Mover copies the event-fragments from the
data-boards to internal memory. Data-Mover memory provides the bulk storage space
required to smooth trigger bursts and data transmission delays.
The Data-Mover has to provide sufficient processing power to allow for an additional
data sparsification loop should that ever
be required by some of the CLEO III sub-components.
The Data-Mover is basically an I/O engine putting a premium on high performance bus
interfaces, fast internal buses and a flexible interface to the outside world, i.e.
our Data-Links. Additional requirements imposed on the Data-Mover include support by a
major real-time operating system such as VxWorks and a network interface.
VME Data-Mover
The VME community has adopted a common standard
for mezzanine cards, PMC, which is electrically compatible with PCI.
PCI offers high performance with a theoretical
throughput of 132 MBytes/s and the
potential for even higher performance (64-bit, 66 MHz) in the near future. Integrated
protocol chips are available and since PCI modules are targeted for a very large market
they are expected to be fairly inexpensive.
We have chosen to base all interconnects
in the CLEO III data collection system
(including the data links to the Event-Builder,
links internal to the Event-Builder,
and the interface to the L3 processor(s))
on the PCI/PMC bus.
VMEbus CPU modules with internal PCI bus and a PMC connector for mezzanine boards
are available for a variety of processor families including DEC Alpha, MIPS, and
IBM/Motorola PowerPC. Overall PowerPC based products offer the best price/performance
ratio and we have chosen this processor line for CLEO III.
Several Motorola MVME1604-002 PowerPC VME modules have been bought
to evaluate data-throughput and to start software development.
While it is questionable that the MVME1604 fulfills all the Data-Mover performance
requirements,
the next generation of these boards will not only contain faster processor chips
but also a direct VME to PCI interface (Newbridge Universe),
on-board FastEthernet (100BaseT), two PMC slots and maybe a 64-bit or 66 MHz
implementation of the PCI bus.
Fastbus Data-Mover:
FRITZ
Picture Gallery (Postscript)
Block Diagram of Data Mover (old)
Block Diagram of Read-Out Software
Front-End Crates
DAQ III Overview
Data-Links
CLEO WEB PAGES
Updated: Nov. 15, 1995
Author: Andreas H. Wolf (ahw@mps.ohio-state.edu)