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3.2 Acyclic Data (Mailboxes)
The mailbox of each communication channel has two areas that are used for non-cyclic message
transfer.
• Send Mailbox
Packet transfer from host system to firmware
• Receive Mailbox
Packet transfer from firmware to host system
The send and receive mailbox areas are used by field bus protocols providing a non-cyclic data
exchange mechanism. Another use of the mailbox system is to allow access to the firmware running
on the netX chip itself for diagnostic and identification purposes. The send mailbox is used to transfer
cyclic data to the network or to the firmware. The receive mailbox is used to transfer cyclic data
from the network or from the firmware.
A send/receive mailbox may or may not be available in the communication channel. It depends on the
function of the firmware whether or not a mailbox is needed. The location of the system mailbox and
the channel mailbox is described in the netX DPM Interface Manual.
Note:
Each mailbox can hold one packet at a time. The netX firmware stores packets that are
not retrieved by the host application in a packet queue. This queue has limited space and
may fill up so new packets maybe lost. To avoid these deadlock situations, it is strongly
recommended to empty the mailbox frequently, even if packets are not expected by the
host application. Unexpected command packets should be returned to the sender with an
Unknown Command in the status field; unexpected reply messages can be discarded.
CANopen Slave |
DOC070901API06EN | Revision 6 | English | 2010-06 | Released | Public © Hilscher, 2006-2010