PCC-IV Instruction Manual (Rev. 0.1)
Page 6-11
Section 6
– Blockware Functions
Technical Reference
F38
[FPT/H] Front Panel Adjustable Track / Hold
Function
FPT/H
is a Track/Hold that allows the Operator to adjust the
Block Output from the Front Panel display when the Block is in Hold
mode. Its function is equivalent to an Auto/Manual, or Remote/Local
station.
Track Mode: When the Block is in Track mode (like Auto or Remote),
the Block Output is set equal to the “Signal” Input. That is, the Block
Output “tracks” the Block Input.
Hold Mode: When the Block is in Hold mode (like Manual or Local),
the Block Output remains at the last value unless changed by the
Operator or the Modbus communications link. In Hold mode, if the
Operator selects a
FPT/H
Block for display on the front panel, the
Block Output can be changed with the front panel UP-DOWN arrows.
After the Operator completes the change, the Block Output will remain at the last value until the next Operator
change or until the Block goes into Track mode. The
FPT/H
Block must have a Tag configured in the Panel Data
Screen to allow changes from the front panel. In Hold mode, the Modbus communications link can change the Block
output by writing a new value to the Block Output.
Mode Selection:
The Track/Hold mode is normally determined by the “Hold Select” Input (0 = Track mode, 1 = Hold
mode). However, the optional Track Override Inputs
can override the “Hold Select” Input. If either “Track Override”
Input is set to a discrete “1”, the “Hold Select” Input is ignored and the Block is forced into the Track mode (see
below). If no Blocks are connected to these Inputs, the default value of Discrete 0 Inputs disable the override feature.
TRACK OVERRIDE 1
TRACK OVERRIDE 2
HOLD
Track/Hold Mode
0
0
0
Track
0
0
1
Hold
0
1
not used
Track
1
0
not used
Track
1
1
not used
Track
Transfer Rate Limiting is OFF when Parameter 3 (Transfer Rate Limit) equals 100%/sec, and the transfer from Hold
mode to Track Mode is instantaneous. That is, the Block Output is set equal to the Signal Input during the first scan
of the mode change.
Transfer Rate Limiting is ON when the Transfer Rate Limit is less than 100%/sec. The rate of change of the Block
Output signal is limited to (Parameter 3) %/sec for the duration of the transfer from the last Hold Mode Block Output
to the current Signal Input. When the Block Output becomes equal to the Signal Input, the rate limiting is disabled
and the Output will track the Signal Input with no rate of change limiting. The Transfer Rate of Change feature is
used primarily to provide bumpless transfer.
In ALL cases, the Block Output is limited to the Min and Max Output values set in Parameters 1 & 2.
For applications that only require a simple Track/Hold function without any Operator adjustment capability, simply
use
FPT/H
without connecting
FPT/H
to a front panel display channel.
At power down, the Block Output is saved in the Retentive Memory area of the NVRAM. During the first scan after
CPU start-up, the
FPT/H
Block Output is set to the value stored in the Retentive Memory.
Output
PV
1
0
1
0
Hold
Xfer Limiting
Time
