Transfer Buffers (Objects 2120-2123); Direct Data Exchange; Prefetch Data Exchange - Bosch Rexroth ID 40 Manual

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Bosch Rexroth AG, MIT: ID 40, 3 842 530 344/2014-05
PROOF COPy 1 | 20.05.2014 | FOR INTERNAL USE ONLy
9.5.4 Transfer buffers (objects 2120–2123)
212x objects are available to transfer buffers for transporting payloads, whereby
x + 1 stands for the number of each transfer buffer. The data type of the objects is
DOMAIN and they can only be read or written by command.
9.5.5

Direct data exchange

It is possible to directly exchange data with an MDT when it is in the CONNECTED
link state (see Chapter 2.2.1 "SLK operating states").
To do this, the buffer mode (subindex 01) in the buffer parameter object of a
selected transfer buffer has to be set to 0x00 and the desired data blocks entered in
the corresponding buffer mapping object.
Reading MDT data: If the CANopen master initiates an SDO upload of the selected
transfer buffer, the SLK retrieves the data blocks indicated in the buffer mapping
from the MDT to execute the SDO request.
Writing MDT data: If the CANopen master initiates an SDO download of the selected
transfer buffer, the SLK enters the transmitted data in the MDT according to the data
areas indicated in the buffer mapping.
During the data exchange, the buffer status register shows the value 0x01, then 0x02
once the exchange is complete. If the buffer status register is mapped in a TPDO
channel, TPDOs are also sent during direct data exchange when the buffer status
changes.
9.5.6

Prefetch data exchange

Prefetch automatically runs in the PRECONNECTED link state, see Chapter 2.2.1
"SLK operating states".
To do this, the buffer mode (subindex 01) in the buffer parameter object of a
selected transfer buffer has to be set to 0x01 and the desired MDT data blocks
entered in the corresponding buffer mapping object.
Once an MDT signs on, the mapped payload is automatically read from the MDT in
the PRECONNECTED link state. Once executed, the data is in the transfer buffer and
the buffer status switches from 0x01 to 0x02. At this point, the SLK sends a TPDO to
the bus master (if the buffer status is mapped) and the application can then retrieve
the transfer buffer by command (via SDO upload).