Rockwell Automation 1771-DMC_DMC1_DMC4_DXPS Control Coprocessor User Manual - Manual (Page 15)

Chapter 1
Introducing the Control Coprocessor
1-5
Control coprocessor
can read/write PLCĆ5
dataĆtable and statusĆ
file information
PLCĆ5
Programmable
Controller
Control Coprocessor
User Memory
PLCĆ5 interface routines
called in a C or BASIC
program
PLCĆ5 controlĆlogic
program (MSG) initiates
communication
PLCĆ5
Programmable
Controller
Control Coprocessor
ControlĆlogic
program using
MSG instruction
Interface routines in C or
BASIC program accept,
interpret, and respond to
PLCĆ5 programmable
controller
discrete I/O read/write
block-transfer
read/write
Important: If a fault occurs in a control coprocessor that is connected to
certain PLC-5 programmable controllers via the side connector, the
programmable controller may be unable to clear the major fault word
without first resetting the control coprocessor. In extreme cases, you may
need to separate the control coprocessor from the programmable controller.
The programmable controllers on which this may be necessary are:
PLC-5/60 (series B revision B)
PLC-5/40 (series B revision B)
PLC-5/30 (series A revision B)
PLC-5/20 (series A revision A)
PLC-5/11 (series A revision A)
Standalone Mode
In standalone mode, you do not connect the control coprocessor directly to
the PLC programmable controller. The control coprocessor can reside in
the same chassis as the programmable controller or in a remote chassis.
Programmable controller
controlĆlogic program
initiates communication
using discreteĆ and/or
blockĆtransfer read and
write instructions
Programmable Controller Control Coprocessor
ControlĆlogic program
using discreteĆ and/or
blockĆtransfer
instructions
Interface routines in C or
BASIC program accept,
interpret, and respond to
programmable controller
The control coprocessor
can initiate directĆaccess
communication to PLCĆ5
user memory as shown here.
You do not need to program
your PLCĆ5 programmable
controller to support these
calls.
A PLCĆ5 controlĆlogic
program can initiate directĆ
access communication to
the control processor as
shown here.
A PLCĆ5 controlĆlogic
program can initiate backĆ
plane communication with
the control processor in directĆ
connect mode via:
Tip
We recommend that you
use 1Ćslot addressing for
standalone mode.
Only the programmable
controller initiates commuĆ
nication with a standalone
control coprocessor.
Communication is via the backĆ
plane using discreteĆ or blockĆ
transfer read/write instructions.