Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 210)

Application Example 2, Periodic Block
Transfer
Appendix C
CĆ26
Table C.C
Recommended Output Annunciators
DESCRIPTION FUNCTION
READ BLOCK TRANSFER
WATCHDOG Indicator
Program Address
012/02
This indicator will illuminate if a read block transfer does not occur within a
predetermined time. The time is determined by the preset value selected for the
timer instruction 043
8
in rung 15 and is userĆselectable. If a read block transfer is
not successfully executed withint the preset time, timer 043
8
will timeĆout and
energize indicator 012/02.
LOAD/ENTER
FAILURE Indicator
Program Address
012/01
This indicator will illuminate in the event of an unsuccessful load/enter sequence.
During program execution, this indicator will normally be off. When a load/enter
sequence is begun, it will illuminate and will remain on until the sequence is
completed (approximately 1 second). If the indicator remains on, then the
load/enter sequence failed. (rung 15).
MANUAL MODE
Indicator
Program Address
012/04
This indicator will illuminiate when the maual control station (if used) is in the
manual mode.
STATUS MONITOR
BYTE ERROR
Indicator
Program Address
012/05
This indicator will show that an alarm condition exists at the module. During
program execution, this indicator will normally be off. If will illuinate when a
condition exists at the module which causes a bit in the status monitor byte to go
high. It will remain on until the error condition is corrected.
NOTE: When this indicator is on, the program will be executing continuou s
load/enter sequences which will allow the source of error be read in the diagnostic
& status words.
Data must be written to the module to correct the problem. Because the program is
executing continuous load/enter sequences, the LOAD/ENTER FAILURE indicator
will be flashing on and off. This condition will occur for any error, read and write
block transfers can be exectued. However no load/enter sequence will be
performed until the soft fault reset bit is set at the module returning the module to
the normal operating mode.
Program for PLCĆ3 Processor
The PLC-3 program for periodic block transfer is presented in Figure 3.7.
Worksheets for the Dynamic Block (Figure C.4figure C.4) and Loop
Blocks (Figure C.5 and NO TAG) also apply to the PLC-3 program. File
storage addresses are listed in Table C.D.