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User's Manual (MUT)
Mod. V895 16 Channel Leading Edge Discriminator
19/03/09
3
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00101/97:V895x.MUTx/03 v895_rev3.doc
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21
4.3. Threshold
setting
Each V895 channel is provided with an 8 bit DAC to set the threshold. The threshold
value can be programmed in a range from -1 mV to -255 mV with 1 mV steps (valid
values: 1÷255).
Threshold for each channel can be set performing a write access to the Base addresses
+ %00 ÷ + %1E (see § 3.2).
4.4. Output pulse width setting
The output pulse width is adjustable from 5 to 40 ns. Two width values can be
programmed: one for channels 0 through 7 and one for channels 8 through 15. Chosen
value is set performing a write access to the following registers (see § 3.4 and § 3.5):
Base + %40
sets output width for channels 0 to 7
Base + %42
sets output width for channels 8 to 15
Valid data for the 8 bit registers are:
0
leads to
5 ns
…
255
leads to
40 ns
with a non-linear relation for intermediate values.
4.5. Updating and Non-Updating mode setting
Each channel of V895 may provide an Updated (retriggerable) or a Non-Updated (not
retriggerable) output. Output mode selection is performed, individually for each channel,
via jumpers as shown in Fig 2.2.
Non-Updating output mode
: an input pulse over threshold occurring at t
1
(event 1 in fig.
4.1) sets the channel output active for the programmed duration T (T=5
÷
40 ns, see
§ 3.4). Any event over threshold occurring at
t
, with t
1
<t<t
1
+T, will be ignored.
Updating output mode
: input pulse over threshold occurring at t
1
(event 1 in fig. 4.1)
sets output active for the programmed duration T (T=5
÷
40 ns, see § 3.4). Any input event
over threshold for t
e
<t
1
+T, will restart the pulse forming stage forcing the output to active
value until instant t
e
+T.