System bus (CAN) with Ser vo PLC & Drive PLC
LenzeCanDrv.lib - Function blocks
9.1 Transmit CAN object (L_CanPdoTransmit)
9-3
L PLC-Systembus EN 1.1
Transmission request memory as an interface between CAN driver and FB
L_CanPdoTransmit
Since data transmission via the CAN driver takes place at the same time as the PLC program is
processed, a temporary storage (transmission request memory) is used between the CAN driver
and the L_CanPdoTransmit FB to store the transmission requests.
L_CanPdoTransmit
L_CanPdoTransmit
Transmit request 1
CAN driver
System bus (CAN)
250 s cyclem
PLC program Operating system
Transmission request memory
L_ParWrite
Transmit request 2
Transmit request 3
Transmit request 64
• Whenever the L_CanPdoTransmit FB is called, a transmission request is saved in the
transmission request memory.
• You can also use the L_ParWrite FB of the LenzeDrive.lib function library to save
transmission requests in the transmission request memory.
• The transmission request memory can temporarily save a total of 64 transmission requests
from the L_CanPdoTransmit or L_ParWrite FB.
• Every 250 µs, the operating system collects a transmission request from the transmission
request memory and processes it at the same time as the PLC program is processed.
Note!
If the L_CanPdoTransmit or L_ParWrite FB is called very often and the transmission request
memory is filled faster than it is emptied by the operating system that collects the transmission
requests, an overrun error occurs.
• With an overrun error, the
nState
variable receives the value -119.
• In addition, the operating system displays an error message.
(See chapter “Error messages” in the Manual for the respective target system.
e.g. 9300 Servo PLC or Drive PLC)
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