Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 166)

Application Example 1, Continuous Block
Transfer
Appendix B
BĆ7
buffer area of the data table (words 233-2548). The rung is conditioned
by the read block transfer done bit 113/07.
When the block length is set to the default value, 00, the instruction
automatically displays a file length of 64 words (words 233-3328).
However, the PID module will only transfer 18 words in a read block
transfer. The remaining 46 words can be used for other purposes such as
timers, counters and word bit storage.
rung 7* Upon completion of a valid read block transfer determined
by examining the block transfer done bit 113/07, the data
from the buffer area is transferred to the status area of the
data table (words 347-3708). Indentifier bits 16 and 17 of
word 2348 are examined for an off condition to ensure that
the data residing in the buffer area is indeed that of the
status block.
rung 8* Timer 0438 is the read block transfer watchdog timer. It
begins timing whenever the read block transfer done bit
113/17 is low. Upon completion of a valid read block
transfer, the done bit goes high and resets the timer. The
preset value of this timer is user-selectable.
rung 9 Annunciator lamp 012/02 illuminated when the read block
transfer watchdog timer times out.
rung 10* The load bit 257/06 is latched when either the power-up
bit 350/13 or store bit 050/00 is high. (Refer to
explanation for rungs 2 thru 4.) When latched, 257/06
initiates a load/enter sequence.
rung 11 The MODULE NOT INITIALIZED indicator 012/03
illuminates when the power-up bit 350/13 is high or the
power-up complete bit 353/04 is low.
rung 12* When energized, the ready bit 350/12 sets the enter bit
257/06.
rung 13* When energized, the ready bit 350/12 sets the enter bit
257/03.