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Data coming from the subdetectors are delivered to the PC over a DT16
Link. In order to get into the SDPC memory, we must convert to PCI.
This is done in two stages as shown below:
The DT2SL interface converts the DT16 into an S-LINK
compliant LDC. We then use an existing S-LINK
to PCI card to interface to the PCI bus on the SDPC. The advantage
of this approach is that the DT16 to S-LINK conversion is relatively simple
- much simpler than building an interface from DT16 to PCI directly. We
can then take advantage of the commercially available S-LINK to PCI card
and of the considerable amount of S-LINK experience and test hardware which
The Status of the Project
15 DT2SL cards have been manufactured (Feb 1998).
15 S-LINK to PCI cards have been delivered from Incaa
Computers (Feb 1998).
Two drivers have been developed and tested using a SLIDAS
test card as well as the DT2SL interface.
The first was based on a Linux
device driver which came from a library generated by Andrea
Cisternino. After disabling of user-space copy this driver achieved
a data rate of 97 MByte/s into
the PC memory.
The production driver was written from scratch. It
is a user-space zero-copy driver which simply maps the S-LINK to PCI card
into memory and then sets up the DMA transfers from the card into the PC
memory. This requires no interrupts and a data rate of 117
MByte/s has been achieved with an infinite
packet size, i.e. the S-LINK card was sending a test pattern of data
continuously with no gaps for protocol.
23 July 1998