SLIC /MBT Tests

SLIC / MBT Tests

Test Description

Updated 10/19/99

Digitized ramps consisting of a series of 256 bytes (00,01,...fe,00) were produced in a Transmitter card at a rate determined by an external pulse generator (we tried 0.1, 1.0, 10, 25 and 40 kHz). This data was sent to the SLIC by hotlink including Begin-Of-Event and End-Of-Event characters. The EOV character used by the transmitter (07) was different than that assumed by the SLIC (08). This should be fixed for future tests, but did not affect this test. Within the SLIC, four bytes of data from the transmitter were concatenated into a single 32-bit word and transmitted on the link to a DSP. The DSP was programmed to store an event's worth of data in internal memory (in this case 256 words, i.e. 4 ramps, because of lack of EOV in the data stream) and then send that data as a block via serial output to the SLIC hotlink output. From the SLIC hotlink output, the data was sent to an MBT hotlink input, and from the MBT to a digital oscilloscope.

Results

Given below are the results of the test for trigger rate of 1.0 kHz and 40 kHz. As a point of comparison, data was first sent from the Transmitter directly to the MBT. The differences between the Transmitter-to-MBT and the Transmitter-to-SLIC-to-MBT results are understood and are explained in the Notes below.

40 kHz Triggers: (10/14/99)

Transmitter-to-MBT-to-Scope
Transmitter-to-SLIC-to-MBT to Scope (note different time scale from 1.)
Transmitter-to-SLIC-to-VME (printout of ramp data received by SLIC for several ramps)

1 kHz Triggers: (10/19/99)

Transmitter-to-MBT-to-Scope:

1 ms/div
2 us/div: MBT (DAC) output to scope shown as trace 1, input to MBT (DAC bit 0) shown on trace 2

Transmitter-to-SLIC-to-MBT to Scope

1 ms/div: Structure of four ramps close together separated by 4 ms is due to only loading an event into the SLIC DSP when 256 words (4 ramps) are present in its buffer.
20 us/div: MBT (DAC) output to scope shown as trace 1, input to MBT (DAC bit 0) shown on trace 2
1 us/div: Traces 1 and 2 as above. Shows the rate that the SLIC writes out data to the hotlink (32 bit words at 500 kHz in the current incarnation - note: this will change in the future). This means that the MBT receives 4 bytes of data at the standard hotlink rate but then must wait for the SLIC to send out the next word for its next four bytes. It explains why the ramp seen on the scope when the SLIC is present in the system is about 10 times slower than without the SLIC.

Transmitter-to-SLIC-to-VME (printout of ramp data received by SLIC for several ramps)

Transmission Error Rates: (10/19/99)
Errors are observed in the data seen in Transmitter-to-SLIC-to-VME mode at rates that depend on the ramp frequency. These errors occur at a low enough rate that it is impossible to tell by observing scope traces whether they are also present in Transmitter-to-SLIC-to-MBT mode. These errors are not unexpected since we have not yet finished optimizing the timing of data transfers on the internal data link and to VME. This is on our list of things to do at Nevis and can be tested with our setup independent of the Transmitter and MBT which are being shipped back to Maryland.