Rockwell Automation 57C445 AutoMax PC Link Interface Module - Manual (Page 39)

D2Ć4
Registers 4 through 7 contain the drop status bits which indicate the
current status of the Network. A 1" indicates that a drop is active and
a 0" indicates that a drop is not active. The status bit for the Master
(drop 0) is maintained as well. Note that the PC Link module
maintains status bits for all drops on the network including its own.
These registers are read only.
Register 12 defines the drop number for the module and
corresponds to the thumbwheel switch on aM/N 57C404 Network
Communications module. After initial module installation, the drop
number is zero. The host application places the desired drop number
in this register. If the number is greater than 0 and less than or equal
to 55, bit 15 will be set to indicate a valid drop number; otherwise bit
14 will be set to indicate an invalid drop number. These status bits are
similar to those used when setting the drop depth on the Network
Communication module. The PC Link module will not go on line"
without a valid drop number. If the drop number is a duplicate of
another active drop on the network, communication errors and
unpredictable communication will result. The drop depth must also
be considered when checking for duplicate nodes.
The diagnostic counters include registers 14Ć19. Register 14
(Messages Received) will increment while the PC Link module is
connected to a Master. Registers 15Ć18 count various communication
errors. These counters are listed in Table 2 in section 2.3.1 of this
appendix. The following are possible causes of communication
errors:
Ć Bad cables or connections
Ć Improper network termination
Ć Any duplicated drops on the network
The host may write to these error registers to clear them at any time.
Register 19 (Messages Transmitted) will be incrementing anytime the
module is responding as an active drop or group of drops.
Register 20 defines the PC Link module drop depth. After initial
module installation, the drop depth is zero. The host places the drop
depth in this register. If the depth number plus the drop number is
less than or equal to 56, bit 15 will be set to indicate a valid drop
depth; otherwise bit 14 will be set to indicate an invalid drop depth.
This is the same as setting the drop depth on the Network
Communications module.
The PC Link module will not go on line" without avalid drop depth.
If the block of drops selected by the drop number and drop depth
duplicates any other active drops on the network, communication
errors and unpredictable communication will result. The module may
be taken off line" at any time by writing zero to register 20.
Register 29 is set by the PC Link module to 6466 decimal, or 1942
hex. This may be used to confirm that a PC Link module is running at
aspecified address.
Registers 32 through 39 are the broadcast data registers. They are
read only and are updated from the Master every 2.6 ms. Broadcast
data register information is sent as part of the update message to
every drop. This means that even in a worst case situation with 56
drops on a network (including the Master) with a total update time of
143 milliseconds (2.6 ms/drop * 55 drops), the broadcast registers
will still be updated by the Master every 2.6 ms.