Rockwell Automation 57C445 AutoMax PC Link Interface Module User Manual

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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.

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.