Rockwell Automation 1757-FFLD Linking Device Configuration Manual - Manual (Page 45)

Publication 1757-PM002A-EN-E - June 2006
Basic Function Blocks 3-7
• QUB: Queued User-triggered Bidirectional
The quantity of each class of VCR that is available for configuration and
communication is device dependent. The quantities are specified in the DD
files, which are provided with each device. An example of the quantities
defined in a DD file, specifically the *.cff file, is shown below.
As can be seen, the quantities are broken into sub-categories depending on
usage. The above example states that the device can have more publisher BNU
than subscriber BNU. Additionally, the device has no client QUB VCR, but it
has the ability to serve 8 server QUB VCR. Currently, these limits manifest
themselves in either download or communication errors when they are
exceeded.
There is also a nuance to the quantities that need to be emphasized with regard
to linking devices. The 1757-FFLD *.cff file is used below as an example.
Table 3.1 : VCR Classes
BNU QUU QUB
Permitted Roles Publisher, Subscriber Source, Sink Client, Server, Peer
Conveyance Paths 1 1 2
Conveyance Policy Buffered Queued Queued
Transmission Policy Network Scheduled User Triggered User Triggered
// From VcrListCharacterisitcs
MaxEntries = 44
NumPermanentEntries = 44
DynamicsSupportedFlag = FALSE //Rev 1.5
StatisticsSupported = 0x0 //Rev 1.5
MaximumNumberOfClientVcrs = 0
MaximumNumberOfServerVcrs = 5
MaximumNumberOfSourceVcrs = 8
MaximumNumberOfSinkVcrs = 0
MaximumNumberOfPublisherVcrs = 19
MaximumNumberOfSubscriberVcr
s = 12
// From VcrListCharacterisitcs
MaxEntries = 44
NumPermanentEntries = 44
DynamicsSupportedFlag = FALSE //Rev 1.5
StatisticsSupported = 0x0 //Rev 1.5
MaximumNumberOfClientVcrs = 0