The trigger bits words indicates which bits were set during the event. The encoding of the bits is the following:

In this section, the following diagram will be used to describe a 16-bit word sent by the Filter. The first row includes the value, either in decimal or hexadecimal format, or a descriptive note. The second row shows the value in binary (“X”s are used to describe arbitrary values that vary from event to event). The last row shows the bit number.

The timestamp is encoded in the XLMV72 time-stamp module for each event as a 64-bit word. The Event Filter parses it as a set of four consecutive 16-bit words.

• Packet Length (self-inclusive)

• Packet Tag

• First 16-bit time-stamp word

• Second 16-bit time-stamp word

• Third 16-bit time-stamp word

• Fourth 16-bit time-stamp word

The event-number is given by the VMUSB scaler channels as a 48-bit word coded in two 32-bit words. The Event Filter parses it and re-formats it as a three 16-bit words.

• Packet Length (self-inclusive)

• Packet Tag

• First 16-bit event-number word

• Second 16-bit event-number word

• Third 16-bit event-number word

The trigger packet includes a bit-pattern word (encoded by the ULM trigger module), with information about what sources triggered the event, and their corresponding time from the Phillips 7186 TDC.

• Packet Length (self-inclusive)

• Packet Tag

• Trigger pattern

the encoding of the active bits is given by the following table:

• Trigger time

The time of each trigger source (except for “coincidences”) is given by a word that look like:

there can be up to four time words (depending on whether time is greater than 0), one for each channel. The channel number Ch is given by:

The time-of-flight packet includes all the timing values encoded in the Phillips TDC and the XFP-FP and OBJ-FP ToF from the ORTEC TACs encoded in the S800 Phillips 7164H ADC.

• Packet Length (self-inclusive)

• Packet Tag

• Time-of-flight values

The time-of-flight information for each channel is coded in words that look like:

Up to eight of these words can be present (depending on wheter time is greater than 0): six from the Phillips TDC, and two from the XFP-FP and OBJ-FP TACs. The channel number Ch is given by:

Note that the time values from the Phillips TDC are subtracted by SpecTcl to the time from the S800 trigger E1 up (encoded in the trigger packet) in order to calculate the corresponding time-of-flight. On the other hand, the times from the TACs (Ch 4 and 5) correspond to actual time-of-flight values.

The scintillator packet includes the energy (encoded in the FERA LeCroy module) and time (encoded in the Phillips TDC) of the S800 FP scintillator signals. In the original configuration, there were 3 scintillators (E1, E2, and E3) which were later reduced to just one (E1) after the installation of the Hodoscope.

• Packet Length (self-inclusive)

• Packet Tag

• Energy and time values

The energy (from the FERA module) and time (from the Phillips TDC) are given by two consecutive words:

These words are sent by the Filter as long as energy is greater than 0 or Ch equals 2. The channel assignment given by the Filter is:

The Ion-chamber packet includes the energies of the 16 ion-chamber segments encoded in one of the Phillips 7164H ADC.

• Packet Length (self-inclusive)

• Packet Tag

• Sub-packet “Energy” Tag

• Sub-packet “Energy” Length (self-inclusive)

• Energy values

The energy (from the Phillips 7164H ADC module) is given by a series of words that look like:

Where Ch is the segment number (from 0 to 15, being segment 0 the most upstream). The Filter gives an energy word for each segment as long as energy is greater than 0.

The Filter provides two CRDC packets: one for Cathode Readout Drift Chambers (CRDC)|CRDC1 and one for Cathode Readout Drift Chambers (CRDC)|CRDC2. Each CRDC packet is divided in two sub-packets: the “Raw” sub-packet with information about the pads energies (encoded in the CRDCs XLM72 modules), and the “Anode” sub-packet with anode energy and time information encoded in the CRDCs Phillips ADC. In the following, we describe the structure of the packet provided by the Filter for each CRDC.

• Packet Length (self-inclusive)

• Packet Tag

• CRDC label

where 0x0000 and 0x0001 identify CRDC1 and CRDC2, respectively.

• CRDC Sub-packet “Raw” Length (self-inclusive)

• CRDC Sub-packet “Raw” Tag

• Dummy word

This word is reserved for a global threshold, which is no longer used.

• Samples sub-packets

The Filter sends a series of sample sub-packets. Each sub-packet consists of two parts. The first part includes one 16-bit word with information about the sample and channel numbers:

where channel is a number between 0 and 63, and refers to a group of four pads. The second part includes up to four consecutive 16-bit words, each with a pad energy greater than 0:

The connector number is related to the pad number (pad) according to: pad = channel + connector x 64 (where connector ranges from 0 to 3, and channel is given by the first word of the sample sub-packet). Note that the Filter processes information from connectors with energies greater than 0.

• CRDC Sub-packet “Anode” Length (self-inclusive)

• CRDC Sub-packet “Anode” Tag