Rockwell Automation AutoMax R-Net Processor Module - Manual (Page 11)

2Ć3
2.2 Electrical Description
Network operation is controlled by a Motorola 68010 CPU/direct
memory access (DMA)/serial I/O architecture. 16K bytes of dualĆport
memory is provided to store the network variables. All program
application data is sent and received by the AutoMax RĆNet
Processor module's CPU. All handshaking, errorĆchecking, and
AutoMate command interpretation is also handled by the AutoMax
RĆNet Processor module; no additional load is put on the main
Processor module(s) for communication.
The module contains a watchdog timer which is enabled when power
is turned on to the module. The onĆboard CPU must reset the
watchdog timer within a specified time or the CPU will shut down and
the READY LED on the faceplate will turn off.
At powerĆup, the red LEDs on the faceplate will turn on as the module
performs a lamp test. The onĆboard CPU then performs diagnostics
on the EPROM, scratchpad RAM, the dual port memory, and the
transmit and receive circuits. The CPU also reads the value of the
node number switches at this time. The red LEDs will light to indicate
which test is being performed. If there is a fault during the diagnostic,
the onĆboard CPU will stop, the watchdog will time out, and the
pattern of the red LEDs will indicate the code of the fault condition.
The fault code is also written to register 60 in the dual port memory. If
all diagnostics are passed, the red LEDs will turn off.
RunĆtime fault conditions detected by the onĆboard CPU after
powerĆup are indicated by fault codes 9Ć15. If a fault is detected, the
READY LED will turn off and the corresponding fault code will be
displayed. The fault code is also written to register 60 in the dual port
memory. All of the above fault conditions are fatal and require that the
rack be powered down and back up to recover.
The red LEDs also signal two nonĆfatal communication errors during
network operation. The top and bottom red LEDs will flash on and off
to indicate a CRC error or lost token timeout, respectively. Refer to
section 5.0 for the procedure used to isolate the cause of a
communication error.
2.2.1 RĆNet Industrial Network
RĆNet is an asynchronous baseband coaxial cable network system
arranged in a multidrop configuration. Network access is granted
using a tokenĆpassing scheme. Each network node controls the
network in turn. When a node has the token, it can transfer data to
any or all nodes on the network. When the transaction is complete,
the token is passed to the next consecutive node on the network.
Data is transmitted over the network via an RGĆ59 or RGĆ11 coaxial
cable at a rate of 800 kilobits per second utilizing the AutoMate
communications protocol. Up to 32 AutoMate controllers and/or other
devices may be connected to the RĆNet network. The maximum
cable length is 6000 feet using RGĆ11/U cable. The minimum cable
length between adjacent drops is 50 feet.