5 — VEHICLE CONTROL LANGUAGE (VCL)
pg. 97
Curtis Model 1351 – December 2018
CREATING AND USING CAN MAILBOXES (VCL SETUP)
CAN Mailboxes are where the 1351 operating system (OS) stores, sends and receive information over
the CANbus. Since there is a limited number of Transmit (TX)
1
and receive (RX)
2
buffers and masks,
CAN mailboxes must be first allocated. The OS provides a handle for each allocated mailbox, which
allows the VCL program to define the mailbox, set it up and use it.
The 1351’s CAN mailbox functions are the same as for the Curtis F-series controllers, and are thus
different than the E/SE series of controllers. The 1351 System Controller differs in the fact it has two
CAN ports that share the available mailboxes and PDO setups between CAN port 1 and CAN port 2.
There are four TPDOs
3
and four RPDOs
4
shared between Port 1 and Port 2. Twenty mailboxes are
available.
In Addition to the normal F series CAN mailbox setup functions, the 1351 offers specific functions
to simplify setting up mailboxes for the CANopen protocol. (The VCL writer may still use the normal
VCL mailbox functions for other protocols or if you require features outside these CANopen specific
functions)
If a CANopen function is used to start the setup of a CAN mailbox, the VCL writer must use only these
CANopen functions for that mailbox. Likewise, these CANopen functions cannot be used with the
normal CAN mailbox function
1
RX (Server to Client), as per CANopen nomenclature. Messages from the master controller to the slave controllers/devices
2
TX (Client to Server), as per CANopen nomenclature. Messages from the slave controllers/devices to the master controller
3
RPDO Receive Process Data Object (RPDO). Data received by the Consumer from Producer communication, (e.g., the master
controller receives PDO data from the slave controller).
4
TPDO Transmit Process Data Object (TPDO). Data transmission by the PDO Producer to PDO Consumer, (e.g., the slave controller
transmits PDO data to the master controller).
Reminder: TX and RX are from the perspective of the slave-device, as per CANopen specifications.
