46
3 SAMPA Chip Implementation
Data Formatting unit does the actual compression and assembling of the data into
either run-length encoded data, with or without cluster sum compression, or Huffman
data. The channel ring buffer consists of an input part and an output part. The input
stores the compressed data from the Data Formatting unit in a ring buffer and attaches
a header to the data once the event is completed. The output retrieves data from the
ring buffer on request from the serialization module. Each channel has a register
bank containing the configuration settings for its filters. The channel register bank is
accessible through the global register.
The trigger distributor takes care of synchronizing the external trigger signals for
each receiving domain. The event trigger signal is delivered to the event manager,
which controls the triggering and distribution of event control signals to all the
channels. An internal 20-bit counter, called the bunch crossing counter, is used for
timestamping of events and can be reset from another external trigger signal (BX
sync trigger). Heartbeat packets are used by the offline system to group events and
check that the front-end device is alive. The transmission of a heartbeat packet is
triggered by yet another external trigger signal (HB trigger).
Up to eleven serialization units can be enabled. Their task is to fetch packets from
either the heartbeat generator, the daisy-chained link, either of the channels, or from
the sync packet generator if no other packet is available. The serializers fetch packets
from the channel in a round-robin fashion according to the channel number, but the
order can be rearranged by configuring a new order in the channel ordering registers.
Several devices can be connected in series in a daisy-chained fashion. A separate
delay compensated serial data input is available for this purpose, together with a
flow control signal to limit the data flow. A daisy chain control module takes care
of synchronizing to the incoming data and controlling the data flow, a separate daisy
chain ring buffer takes care of storing the data in the buffer, making it ready to be
retransmitted by the serializer.
For applications with less complex needs, the data can be serialized directly from
the ADC inputs by an independently operating Direct ADC serializer module.
3.2.1 System Services
This section describes the clocking and reset functionality of the device.
3.2.1.1 Clock Management
The SAMPA device requires several clocks internally to be able to serialize the
relatively slow parallel input data from the 32 ADCs at high output data rates. As
mentioned in Sect. 2.4.2, the device is intended to be operated in conjunction with
the GBTx chip, which has three options for data serialization speeds, 320, 160, and
80 Mbps. Clocks are supplied from the GBTx at the corresponding frequencies as
well.
3 SAMPA Chip Implementation
Data Formatting unit does the actual compression and assembling of the data into
either run-length encoded data, with or without cluster sum compression, or Huffman
data. The channel ring buffer consists of an input part and an output part. The input
stores the compressed data from the Data Formatting unit in a ring buffer and attaches
a header to the data once the event is completed. The output retrieves data from the
ring buffer on request from the serialization module. Each channel has a register
bank containing the configuration settings for its filters. The channel register bank is
accessible through the global register.
The trigger distributor takes care of synchronizing the external trigger signals for
each receiving domain. The event trigger signal is delivered to the event manager,
which controls the triggering and distribution of event control signals to all the
channels. An internal 20-bit counter, called the bunch crossing counter, is used for
timestamping of events and can be reset from another external trigger signal (BX
sync trigger). Heartbeat packets are used by the offline system to group events and
check that the front-end device is alive. The transmission of a heartbeat packet is
triggered by yet another external trigger signal (HB trigger).
Up to eleven serialization units can be enabled. Their task is to fetch packets from
either the heartbeat generator, the daisy-chained link, either of the channels, or from
the sync packet generator if no other packet is available. The serializers fetch packets
from the channel in a round-robin fashion according to the channel number, but the
order can be rearranged by configuring a new order in the channel ordering registers.
Several devices can be connected in series in a daisy-chained fashion. A separate
delay compensated serial data input is available for this purpose, together with a
flow control signal to limit the data flow. A daisy chain control module takes care
of synchronizing to the incoming data and controlling the data flow, a separate daisy
chain ring buffer takes care of storing the data in the buffer, making it ready to be
retransmitted by the serializer.
For applications with less complex needs, the data can be serialized directly from
the ADC inputs by an independently operating Direct ADC serializer module.
3.2.1 System Services
This section describes the clocking and reset functionality of the device.
3.2.1.1 Clock Management
The SAMPA device requires several clocks internally to be able to serialize the
relatively slow parallel input data from the 32 ADCs at high output data rates. As
mentioned in Sect. 2.4.2, the device is intended to be operated in conjunction with
the GBTx chip, which has three options for data serialization speeds, 320, 160, and
80 Mbps. Clocks are supplied from the GBTx at the corresponding frequencies as
well.