Rockwell Automation 57C329 Remote I/O Communications, AutoMax - Manual (Page 65)

4Ć3
D The module must be memoryĆmapped, not I/O mapped.
D The module must support 16Ćbit data transfers.
D Interrupts will be ignored.
D Input and output registers must be located at separate addresses.
Modules that do not have separate addresses will be considered
output modules.
4.4 Data Transmission
At power up, the master will poll all of the slave drops to determine
which drops are connected to the network and the total number of
Multibus modules in each drop. You can assign Multibus slave drop
numbers (1 through 7) or (9 through F for Shark digital racks)
arbitrarily, but each drop must have a unique number. The physical
order of drop connections has no effect on the system.
Through the Multibus backplane, the slave Remote I/O module
collects and stores input and output data associated with up to 15
general purpose I/O modules in its remote rack. The Shark Interface
module collects I/O data from up to 10 modules in its remote rack(s).
The Remote I/O Head collects I/O data from up to 128 2Ćbit modules
in its attached rails. The Remote Drive Interface Head collects I/O
data from up to four drives. This data is sent to the master Remote
I/O module when it polls the slave drop.
The master module collects and stores the data in its dual port
memory, which is accessible to the Processor module in the master
rack. After polling all active slave drops, the master then polls one
inactive drop to determine whether or not another drop has been
added to the network. If a response is received, the new drop will be
added to the list of active drops. The cycle then repeats.
All messages are checked for correctness by the receiving drop.
Messages received in error are reĆtransmitted up to three times.
Drops unable to correctly transmit and receive data will go offĆline.
Status information about the slave drops is maintained in the master
and can be accessed by applications tasks or the Monitor function in
the AutoMax Programming Executive software.
4.5 Data Update Rate
The time required for the master Remote I/O module to update all of
the registers in one slave drop is dependent on the number of
registers being transferred to/from each slave on the Remote I/O
network, i.e., the total number of I/O in the rack.
The update time for each I/O register on the Remote I/O network is
equal to the time needed to service each slave drop plus the amount
of time required by system overhead.
The time required to service each slave drop (DROP_TIME) can be
calculated as follows:
For a Multibus rack slave drop,
DROP_TIME = [1.5 + (N x 0.018)] milliseconds
where: N = Total number of registers being transferred to/from
the slave drop