CAEN V775 TDC

Media:Manual_CAEN_775_TDC.pdf

The 12 bit ADC conversion time is 5.7 \mu s. A sliding scale technique is used to reduce differential nonlinearity by injecting an offset. This reduces the dynamic range to 0->3840. The ADC values between 3841 and 4095 indicate an error.

Address
Pin	Setting
SW 1	1
SW 2	6
SW 3	0
SW 4	8

initialize TDC

-> c775Init(0x610000)
Initialized TDC ID 0 at address 0x90610000 

Common Start/Stop =

BitSet 2 is used to set the TDC in common start or stop mode.

0 => common start
1 => common start

Use the Status function to see what the bit is set at

-> c775Status(0)
STATUS for TDC id 0 at base address 0x90610000 
---------------------------------------------- 
Interrupts Disabled
Last Interrupt Count    : 0 
            --1--  --2--
 Status  = 0x0050 0x0002
 BitSet  = 0x0000 0x0898
 Control = 0x0000
 FSR     = 140 nsec
 Event Count     = (No Events Taken)
 Last Event Read = (No Events Read)
value = 37 = 0x25 = '%'

BitSet 2 is set to 0x0898 = 100010011000 d

The above has bit 10 ( starting from 0 at the very left) set to 0 => common start

Read Data

Use PrintEvent to print out the data in the TDC to the ROC console

-> c775PrintEvent
 TDC DATA for Module 0
 Header: 0xfa000100   nWords = 1 
     0xf80048b8
 Trailer: 0xfc00005a   Event Count = 90 
value = 3 = 0x3

Decoding the data

Header

Header = 0xfa000100 = 11111010000000000000000100000000 b

bits 27-31 contain the GEO address = 11111 d = 0xF

bits 26-24 contain the type of word 010 => header

bits 16-23 contain the crate number = 00000000 => crate 0

bits 8-13 contain the number of channels contained in the data word = 000001 = 1 TDC channel

Data Words

data = 0xf80048b8 = 11111000000000000100100010111000 b

bits 27-31 contain the GEO address = 11111 d = 0xF

bits 26-24 contain the type of word 000 => dataum

bits 16-20 contain the channel number = 00000 => channel 0

bit 14 = data valid bit = 1 => valid data

bit 13 = underthreshold bit

bit 12 = overflow bit 0 => ADC not in overflow

bits 0-11 contain the TDC value = 100010111000 b = 0x8b8 = 2232 d

The TDC value for channel 0 is 2232 channels.

The manuals says the TDC has a range from 140 ns to 1.2 \mu s with 8 bit resolution.

The Trailer structure

Trailer: 0xfc00005a   Event Count = 90

Measureing the TDC range

I used the Stanford pulse generator to generate 2 NIM pulses and then sent those to a NIM to ECL converter in order to create 2 ECL pulses which the TDC accepts as input.

I set the delays to

A = T+0

B = T+ 60 ns

C = T+ 70 ns

D = T + 130 ns

The TDC data bits were = 010000100001 b = 1057 d

Change the delays on "C" and "D" to:

A = T+0

B = T+ 60 ns

C = T+ 100 ns

D = T + 150 ns

And the TDC bits become = 010111010001 b = 1489 d

Change the delays on "C" and "D" to:

A = T+0

B = T+ 60 ns

C = T+ 150 ns

D = T + 200 ns

TDC bits = 100110010011 b = 2451 d

Change the delays on "C" and "D" to:

A = T+0

B = T+ 60 ns

C = T+ 200 ns

D = T + 250 ns

The TDC can only measure time intervals up to about 250 ns.

For Channel 0 I injected the pulses

10111110110 b = 1526 d

Data = 0xf80048b1 = 11111000000000000100100010110001 b

bits 0-11 = 100010110001 b = 2225 d = 0x 8b1

200 px

EOB / Trailer

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