Installation manual

Publication 1747-RM001G-EN-P - November 2008
B-18 SLC Status File
S:2/15 Dynamic
Config
Communications Servicing Selection Bit
(Ethernet Channel 1 for SLC 5/05)
(DH+ Channel 1 for SLC 5/04)
(DH-485 Channel 1 for SLC 5/03)
••••
When set, only one communication request/command can be
serviced per END, TND, REF, or SVC. When clear, all
serviceable incoming or outgoing communication
requests/commands can be serviced per END, TND, REF, or
SVC. When clear, communication throughput increases.
However, your scan time will increase if several
communication requests/commands are received in the same
scan.
One communication request/command consists of either an
incoming command, a message reply, or an outgoing message
command. See S:2/5, S:2/6, and S:2/7 and S:33/7.
To program this feature, use the Data Monitor function to set
or clear this bit. To provide protection from inadvertent data
monitor alteration of your selection, program an unconditional
OTL instruction at address S:2/15 to ensure one
request/command operation, or program an unconditional OTU
instruction at address S:2/15 to ensure multiple
request/command operation. Alternately, your program may
change the state of this bit using ladder logic if your
application requires dynamic selection of this function.
Application example: Suppose you have a system consisting
of an SLC 5/03 processor, programming software, and a DTAM.
The program scan time for your user program is extremely long.
Because of this, the programming device or DTAM takes an
unusually long time to update its screen. Improve this update
time by clearing S:2/15.
In a case such as this, the additional time spent by the
processor to service all communication at the end of the scan
is insignificant compared to the time it takes to complete one
scan. You could increase communication throughput even
further by using an SVC instruction. See page 12-3 in this
manual for more information.
Table B.2 Status File Functions (Continued)
Address Classification Description Fixed
5/01
5/02 5/03 5/04 5/05