Table of Contents
Advertisement
Firmware 95000405 and later, offers additionally an option to buffer regular data and scaler
data in common data buffers. This option is selected by setting bit 5 of Global Mode Register
to "1" and it allows one to avoid short buffers, which tend to waste the USB bandwidth. In
mixed buffers, scaler events are identified by bit 15 set in the event header word. The global
mode register for firmware 95000405 and later has the following 16-bit structure.
Bits
15
Value
-
BusReq
The BuffOpt bits (0-3) define the output buffer length. Bit 4 controls the mode of buffer
filling, such that 0 closes buffers at event boundaries and 1 allows spreading events across
the adjacent buffers:
BuffOpt Value
0
1
2
3
4
5
6
7
8
9
The MixtBuff=1 selects mixed buffer option which allows one to pack data associated with
different triggers (NIM, scaler, IRQs) into the same data buffers. In mixed buffers, events
associated with different triggers are identified by an Event Type ID encoded in bits 13-15 of
the event header word. Note that the bits 0 to 11 of this word list the event length and bit 12
indicates event length exceeding the length of the 2k Word event assembly buffer (i.e., that
the event is to be continued in next event buffer).
The EvtSepOpt sets the number of event terminator words (hexadecimal 5555 and AAAA),
such that EvtSepOpt=0/1 cause one/two terminator word/s written at the end of each event.
The Align32 bit controls the alignment of data in the data buffer. The default alignment
(Align32=0) is on 16-bit boundaries. Setting Align32=1 causes all header (buffer and event)
and terminator words to be converted to 32-bit words, by adding blank 16-bit words. Also
16-bit data words that may be returned by some VME read commands are converted to 32-bit
numbers.
The HeaderOpt bit controls the structure of the buffer header, such that HeaderOpt=0 writes
out one header word identifying the buffer type (bit 15=1 – watchdog buffer, bit 14=0 – data
buffer, bit 14=1 – scaler buffer) and the number of events in buffer. When HeaderOpt = 1,
the second header word is written out listing the number of words in the buffer.
The BusReq bits identify the VME Bus Request level (0 to 4) to be used by VM-USB, when
not operated as a slot 1 controller (bus arbiter). BusReq=1,2,3, and 4 cause BR0, BR1, BR2,
and BR3 lines to be used, respectively.
WIENER, Plein & Baus GmbH
12-14
9-11
-
HeaderOpt
Buffer Length (words)
13k (default)
8k
4k
2k
1k = 1024
512
256
128
64
Single Event
8
7
Align32
EvtSepOpt
17
6
5
MixtBuff
www.wiener-d.com
4
3 - 1
B u f f O p t
Advertisement
Table of Contents
