rotork Mk3 - Discrete Input Blocks

Actuator Input Output Signals
Publication PUB089-005-00_0618 61 of 116
6.4 Discrete Input blocks
There are five Discrete Input Blocks (DI) included on the FF CP card. These DIs are preconfigured to
read back information from actuator. The description of each reported data bit is included in section 5.
The value reported by each DI block is in the range 0-255. This can be split into 8 discrete binary
values, allowing 8 different signals to be reported within each block. The host DCS will need to decode
the number into its binary parts using a Boolean Fan In function. In this way the operator can access a
large number of discrete signals using a minimum number of function blocks.
If the host system is not able to support the Boolean function, the first bit in each block represents a
different actuator feedback signal and all 5 blocks can be used to transmit 5 bits of discrete data.
The use of Boolean functions will maximise the data transmitted with the minimum of network
resources.
The bit information contained in the first bit of each block is as follows:
 DI 1 Single bit (bit 0) status = Actuator at Close Limit.
 DI 2 Single bit (bit 0) status = Actuator at Open Limit
 DI 3 Single bit (bit 0) status = Actuator selector in Remote.
 DI 4 Single bit (bit 0) status = Actuator has a General Alarm.
 DI 5 Single bit (bit 0) status = Actuator is moving.
The information from each block is shown below.
Block
Bit
Operation
DI 1
0
1
2
3
4
5
6
7
Close limit
Open limit
Actuator moving
Actuator closing
Actuator opening
Selector In Remote (Selector in “Run” on a CVA)
Selector In Local Stop (Selector in “Stop” on a CVA)
Selector In Local (Selector in “Test” on a CVA *)
Fig 6.6: Discrete Input Function Block
DI
Transducer
Out
SIMULATE
OPTIONAL
INVERT
OUTPUT
PF_TIME