Siemens Sinumerik 810T - Manual (Page 190)

09.91 3 Operating Sequences
3.1.15 Data input/data output
Circular buffer
The circular buffer is located in the part program memory and stores program sections loaded
via the interface.
The use of this circular buffer reduces the amount of memory available for part programs to be
edited. The size of the circular buffer is defined on installation in an NC machine data. Then
the part program memory has to be newly formatted. The circular buffer contains up to two
programs, which can be processed in two ways:
• If only one part program or parts therefore are in the circular buffer, normal block transfer
mode is used.
• If the circular buffer contains two part programs, they can be processed one after another
with NC start. While the first program is being executed the second program can be load-
ed into the buffer. If the first program has terminated, the second program can be started
and third program loaded into the buffer. You determine when which program can be read
into the buffer and executed. Unlike in the part program memory, in the circular buffer a
program once executed is discarded to make room for the next program to be loaded. A
reorganization of the buffer like that of the part program memory is therefore obviated.
Data can be transferred between the peripheral device and the NC in two ways.
• Unprotected transmission
Unprotected transmission of data for the “BLOCK TRANSFER” function is controlled by the
NC using the XON/XOFF interface signals. The NC initiates data transfer from the storage
device by sending an XON. The external storage medium then sends data to the NC until the
circular buffer is full (free are < 120 bytes) and the NC interrupts the data flow with the XOFF
signal. If the circular buffer becomes empty again, the NC sends the XON signal and
transmission is continued.
• Protected transmission
Via NC machine data 5016.0 you can define whether the data is to be transferred protected
or unprotected from the peripheral devices. If you have selected protected transmission of
data (bit set to “1”), the 3964R procedure is activated when data transfer is initiated. After NC
start, the control sends a command block (initialization block) to the peripheral device. The
command block contains the required program number so that after receiving this command
block the peripheral device begins with the transmission of the data. Should you require more
detailed information on data transmission, please refer to the “Installation Instructions.”
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SINUMERIK 810T, GA3 (BN)