Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 30)

Publication 1757-UM006A-EN-P - May 2002
1-16 The Fieldbus Communication Model
Table 1.G Control Selector Block Specifications
Description The Control Selector function block accepts input from up to three control signals and selects one for output based on
the SEL_TYPE setting of High, Middle, or Low. A functional schematic of the block is shown in Figure 1.7 for reference.
Function Notes • All inputs must have the same scaling as OUT, since any one can be selected for OUT.
• Supports Out of Service (OOS), Initialization Manual (IMan) Local Override (LO), Manual (Man), and Automatic
(Auto) modes.
• If an input has a sub-status of Do Not Select, it will not be selected.
• Three separate back calculation outputs (BKCAL_SEL_1, 2, 3) are available - one for each input (SEL_1, 2, 3).
• The status will identify those inputs that are not selected. Control signals that are not selected are limited in one
direction only as determined by the SEL_TYPE selection.
• The value of each BKCAL_SEL_1, 2, 3 output is the same as OUT. The limits of back calculation outputs
corresponding to not-selected inputs will be high for a low selection, low for a high selection, or one of each for a
middle selection.
• If the status of an input is Bad, it is not eligible for selection. If the status of an input is Uncertain, it is treated as
Bad unless the STATUS_OPTS selection is Use Uncertain as Good.
• When all inputs are Bad, the actual mode goes to Manual. This condition will set Initiate Failsafe (IFS) in the output
status, if the STATUS_OPTS setting is IFS if BAD IN.
• If SEL_TYPE selection is Middle and only two inputs are good, the higher input will be selected.
• If the status of BKCAL_IN is Not Invited (NI) or Initialization Request (IR), it is passed back on all three back
calculation outputs. This causes all initializable inputs to initialize to the BKCAL_IN value. Otherwise, if the status
of BKCAL_IN is not normal, it is passed back on the BKCAL_SEL_N, where N is the number of the selected input.
The back calculation outputs for not-selected inputs just have the Not Selected status with the appropriate high or
low limit set.
• When the mode is Manual, no input is selected. All three back calculation outputs will have a Not Invited status
and Constant limits, with a value equal to OUT.
Parameters
(see Appendix A
for definitions of
each parameter) ALERT_KEY
BKCAL_IN
BKCAL_SEL_1
BKCAL_SEL_2
BKCAL_SEL_3
BLOCK_ALM BLOCK_ERR
GRANT_DENY
MODE_BLK
OUT
OUT_HI_LIM
OUT_LO_LIM OUT_SCALE
SEL_1
SEL_2
SEL_3
SEL_TYPE
ST_REV STATUS_OPTS
STRATEGY
TAG_DESC
UPDATE_EVT