Automation Direct D2-DCM, Руководство пользователя

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B–9
B–9
RLL Communications Programs
Data Communications Module, 2nd Edition, 2/03
Controlling the communications
Y50
Set
SP125
SP124
LD
K201
LD
K3
LDA
O40600
RX
Y0
Whenever communication is executed with a
D2–DCM, chances are the communication will
take longer than the actual PLC scan. If the
D2–DCM is busy, another request should not
be initiated until it is finished. Fortunately,
there is an easy solution for this.
There are two SPs for each slot in the CPU
base which are used only with the D2–DCM.
For example, slot 0 has SP120 and SP121.
SP120 is the D2–DCM Busy relay and, when
turned on, indicates the D2–DCM is busy.
SP121 indicates there is a communication
error for slot 0.
You should always use the D2–DCM Busy SP
in your RLL programs to ensure the D2–DCM
is ready.
The communication error SP is optional, but it
is a good way to monitor the communication
status in the RLL program. If you use the
communication error SP, make sure you place
it at the beginning of your communication
routines. This is because the communication
error relay is always reset (turned off)
whenever an RX or WX instruction is
executed.
D2–DCM
Busy
Communication Error
DL205
CPU
0 1 2 3 4 5 6
Special Purpose Communication Relays
Communication Busy
Communication Error N/A SP122 SP124 SP126 SP130 SP132 SP134 SP136
N/A SP123 SP125SP127 SP131 SP133 SP135SP137
7
I/O Slot Location 0 1 2 3 4 5 6 7
Communications
Special Relays