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SIS Documentation
SIS3820
VME Scaler
Page 71 of 79
If the modules contain no scaler data (FIFO is empty), the resulting VME data will look like
shown below.
32-bit data word
Content
Comment
1
0x08000000
Header module 1, Geo 1
2
0x08000008
Trailer module 1, 8 Bytes
3
0x10000000
Header module 2, Geo 2
4
0x10000008
Trailer module 2, 8 Bytes
5
0x18000000
Header module 3, Geo 3
6
0x18000008
Trailer module 3, 8 Bytes
7
0x20000000
Header module 4, Geo 4
8
0x21000008
Trailer module 4, Status: Last module, 8 Bytes
15.9.2 CBLT hints
While it is trivial to setup a block of modules for CBLT readout, one has to be aware of
specialities of this readout form.
•
The user has to make sure, that the read access to the CBLT address is a BLT32 block
transfer (with address modifier AM=0xB or AM=0xF), i.e. the modules will not respond
to a read, which is broken down into many single reads (AM 0x9 e.g.). This can be
verified with a VME diagnosis module like the VDIS or with an oscilloscope and an
extender.
•
The requested number of bytes of the CBLT transfer have to be higher than the max.
number of bytes of the readout data of all participated modules. This ensures that the Last
module terminates the CBLT transfer with a BERR* signal. All other participated
modules monitor a BERR* occurring and then they terminate the CBLT transfer. All
modules are now ready for the next event.
•
In many cases the block size will not be known, as it may depend on the number of hits in
an ADC or TDC. In that case the user will have to setup a CBLT with the number of
possible words and rely on the capability of a block transfer terminated by a VME bus
error and a returned Byte count to indicate the actual length of the transfer.
15.10 Broadcast
Broadcast is a way to distribute a signal like LNE with minimum jitter and latency to a
number of SIS3820 units over VME. Broadcast uses the same setup as CBLT. Broadcast
addressing uses the CBLT address plus the offset of the given key address to invoke the
corresponding action. An example will be made available shortly.