Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 102)

Programming
Chapter 3
3Ć59
B14, B12, B11 defined in section titled Dynamic Block: Words
W01-W17.
Status Monitor Byte
The status monitor byte, SMB, allows the status of the PID module to be
reported without performing a read block transfer. By using the status
monitor byte it is possible to examine the general status of the PID
module. Whenever a block transfer is not being requested, the status
monitor byte data is transferred to the input image area of the PC data
table designated by the rack number, module group number, and lower
slot number of the PID module.
Bits B04-B00 are used to report module status. Bits B07-B05 are used to
precondition the status bits to ensure their validity.
NOTE: The user program should monitor the preconditioned bits
B04-B00 to enable a read block transfer of the status block whenever an
SMB status bit goes high.
The SMB bits are defined below and are illustrated in Figure 3.19. An
example of preconditioning is illustrated in Figure 3.20.
SMB B07 Precondition. Set to 1 indicates the byte is invalid. Reset
to 0 when the byte is valid.
SMB B06 Precondition. Set to 1 indicates the byte is invalid. Reset
to 0 when the byte is valid.
SMB B05 Precondition. Set to 1 indicates the byte is valid. Reset to
0 when the byte is invalid.
SMB B04 Alarm. Set to 1 when an alarm condition exists as
reported by the loop status word W61(W68). Reset to 0 indicates no
alarm condition have been detected. The alarm conditions and
corresponding status bits which set SMB B04 =1 are listed in table 3.K.
Also, SMB B04 will be set to 1 if the dynamic block error bit
W58 B15 or the loop block error bit W58 B14 is set to 1.
Then the loop time/diagnostic bit W01 B07 should be set
high (concurrently) so that the diagnostic data in word W60
can be reported.