User manual

PID Loop Operation
(DL450 Only)
Maintenance
and Troubleshooting
8--58
PID Loop Operation (DL450 only)
DL405 User Manual, 4th Edition, Rev. A
Many applications do not require all 16 R/S steps. Use all zeros in the table for
unused steps. The R/S generator ends the profile when it finds ramp slope = 0.
The individual bit definitions of the Ramp/Soak Table Flag (Addr+33) word is listed in
the following table.
Bit Ramp/Soak Flag Bit Description Read/Write Bit=0 Bit=1
0 Start Ramp/Soak Profile write --
0¤1Start
1 Hold Ramp/Soak Profile write --
0¤1Hold
2 Resume Ramp/soak Profile write --
0¤1
Resume
3 Jog Ramp/Soak Profile write --
0¤1Jog
4 Ramp/Soak Profile Complete read -- Complete
5 PV Input Ramp/Soak Deviation read Off On
6 Ramp/Soak Profile in Hold read Off On
7 Reserved read Off On
8--15 Current Step in R/S Profile read decode as byte (hex)
The main enable control to permit ramp/soak
generation of the SP value is accomplished with
bits 11 in the PID Mode 1 Setting V+00 word, as
shown to the right. The other ramp/soak controls
in V+33 shown in the table above will not oper-
ate unless this bit=1 during the entire ramp/soak
process.
The four main controls for the ramp/soak generator
are in bits 0 to 3 of the ramp/soak settings word in
the loop parameter table. DirectSOFT controls
these bits directly from the ramp/soak settings dia-
log. However, you must use ladder logic to control
these bits during program execution. We recom-
mend using the bit--of--word instructions.
Ladder logic must set a control bit to a “1“ to command the corresponding function.
When the loop controller reads the ramp/soak value, it automatically turns off the bit
for y ou. Therefore, a reset of the bit is not required when the CPU is in Run Mode.
The example program rung to the right shows
how an external switch X0 can turn on and the
PD contact uses the leading edge to set the
proper control bit to start the ramp soak profile.
This uses the Set Bit--of--Word instruction.
Ramp/Soak Table
Flags
Ramp/Soak
Generator Enable
Ramp/Soak
Controls