BECKHOFF C1220 - Manual (Page 18)

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Software description of functions 18
Beckhoff Lightbus - PC interface card C1220
where: aa 00 = start of a CDL transfer
01 = further descriptors of the same CDL
02 = last transfer of the same CDL
bb Process image No bb ( 1 ... 8)
db1,0 Descriptor 1, byte 0 of a CDL
... ...
dbn,19 Descriptor n, byte 19 of a CDL (n = 2 ... 13 )
The module address, the control byte and the pointers to the data bytes of
a message are transferred in Intel notation (least significant byte at least
significant address).If a pointer to a data byte in a message is not needed,
a dummy pointer 0x0ffff
must be entered here.
The arguments 2 - n can be dropped when CDL transfer is concluded
(Argument aa = 02).
Freely programmable communication
With this mode of communication, telegrams are stored as from a
previously defined address in the DPRAM and are combined in a process
image. The input data is transferred to the PC system as from an address
that is also defined beforehand.
With this function, the parameters necessary for initialization are
transferred to the C1220.
Argument Channel Length Function blank
0 1 2 3
Request 09 0x0b 00 pan at oa 0,1 ia 0,1
Channel Length Function Argument 0 Comment
Reply 03 0x0b 00 ok
03 0x0b 01 Error
where: pan Process image number
at Number of telegrams
oa 0,1 Base address of output area
ia 0,1 Base address of input area
The base address of the output area defines the memory area in the
DPRAM as from which the user-defined telegrams are stored. In doing so,
only the address byte, the control byte and four data bytes are entered.
The check byte is not entered. This entry is made internally by the
controller.
As from the base address for the input area, the C1220 enters 0x00 for the
address and control byte and the input data is stored.