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Data Acquisition Overview
6.1.2
PUSH Mode
The SLAVE mode can sometimes cause a lot of delays due to Nagle Algorithm when the number of
shots to acquire is very low (like in the case of single shot acquisition mode) due to the large number
of small sized commands being issued. In order to overcome this the PUSH mode was introduced. In
this mode, the detector takes on the roll of the MASTER and the client acts as the SLAVE. The detector
is by default initialized to operate in the SLAVE mode after powering on. The PUSH mode is activated
only when the PUSH flag is used along with the START command. Once the PUSH mode is activated,
the detector does not need any additional commands for data acquisition. It transmits the data once
the predetermined number of shots are acquired and automatically restarts the detector for the next
acquisition cycle. The PUSH mode makes use of a separate PUSH Socket in order to send data to
the client. The PUSH Socket is on the port COMMAND Socket + 1 and hence the default port for
the PUSH Socket is 2056. The PUSH Socket is a unidirectional communication socket. It is only
used to send the acquisition data from the detector to the client. All commands sent to the detector
should be on the COMMAND Socket and the client can not use the PUSH Socket for any purpose
other than to receive the data.
Once the detector is put into the PUSH mode it starts the acquisition of the requested shots, transmits
it on the PUSH Socket once the acquisition is completed and restarts itself for the acquisition of
the next cycle. This process loops until a STOP command is sent by the client on the COMMAND
Socket. The STOP command disables the PUSH mode and sets the detector back into the SLAVE
mode. Please refer to the section on Efficient use of SP32 for Data Acquisition for
more information on when to make use of the PUSH mode. The typical steps involved in acquiring
data from the detector in the PUSH mode are :
• Step 1 → TCP/IP Connection : Open up a connection to the COMMAND Socket and PUSH
Socket on the corresponding ports. The detector makes use of the COMMAND Socket to
receive commands and send replies. The PUSH Socket is used to send acquisition status
and data to the client.
• Step 2 → Step 7 : These steps are exactly the same as in the SLAVE mode Operation.
• Step 6 → Start : Issue a START command for an acquisition of the required number of shots capable of being averaged internally along with the PUSH flag enabled. The maximum shots capable of being averaged internally is determined by the HW? command reply by the MaxPushShots
parameter. The PUSH mode is only enabled after the START command is sent with the PUSH
flag. Once the PUSH mode is enabled, all the client has to do is read and process the incoming
data on the PUSH Socket.
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