Long term, error free, full duplex transmission was established, utilising two
RCube evaluation boards, with the Bullit chips operating at a clock frequency
of 64 MHz and the RCube switches running with a 66 MHz and a 60 MHz clock respectively.
All links of each RCube were in operation for this test and AC coupling was
used between the boards. The measured data rate was 58 Mbyte/s. The latency
for sending the data from one Bullit to the other traversing each RCube four
times was 
. The packet latency across the RCube has been measured
to be 180 ns at 66 MHz, which corresponds to 12 clock cycles.
During longer term runs of over 48 hours more than 180 terabytes of data were
transmitted without errors for a number of different combinations of cables,
clocks and power supply voltages. This results in a bit error rate better than
. The main problems to overcome to achieve this result
were related to the external control logic which has to handle asynchronous
FIFO signals without any metastable conditions.
A few problems with the current HS-Link devices have been found during the testing: the Bullit keeps the EP character in its transmits FIFO until the next character is written into it, the necessity to take the RCube links out of reset synchronously and the HS-Link initialisation in a mixed Bullit and RCube system. Workarounds for these and other problems have been elaborated.