IS220PDIAH1A - Discrete Input Module

IS220PDIAH1A - Discrete Input Module IS220PDIAH1A - Discrete Input Module

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Part Number: IS220PDIAH1A
Manufacturer: General Electric
Product Type: Discrete Input Module
Function: I/O Module
Series: Mark VIe
Number of channels: 24 dry contact voltage input channels
Input isolation in pack: Optical isolation to 1500 V on all inputs
Input Filter: Hardware Filter, 4 ms
AC Voltage Rejection: 60 V RMS at 50/60 Hz at 125 V dc excitation
Availability: In Stock
Country of Origin: USA

IS220PDIAH1A is a Discrete Input Module manufactured by General Electric as part of the Mark VIe series used in gas turbine control systems. The electrical link between one or two I/O Ethernet networks and a discrete input terminal board is provided by the Discrete Input (PDIA) pack. A processor board that is shared by all Mark* VIe distributed I/O packs and an acquisition board designed specifically for the discrete input function are both included in the pack. The pack supports up to 24 contact inputs, as well as feedback signals particular to the terminal board and PDIA (with types TBCIH1, H2, and H3 terminal boards). There are connections for the type TICI isolated discrete input board with voltage sensing. Dual RJ45 Ethernet ports and a three-pin power input provide the system input to the battery pack. A related terminal board connector and a DC-37 pin connector are immediately connected for discrete signal input. 

Discrete Input Module

The DIN-rail mounted DTCI board is incompatible with PDIAH1A, however it is compatible with the other four types of discrete contact input terminal boards, including TBCI, TICI, and STCI. The compatibility information is provided in the table below:

Terminal Board Discrete Input

  • One I/O pack and one or two network connections are used in simplex.
  • Two I/O packs with one or two network connections are used by Dual.
  • Three I/O packs with one network connection each are used by TMR.

How to Install a PDIA Pack?

  1. Mount the selected terminal board firmly.
  2. Directly connect the PDIA I/O pack to the connections on the terminal board.
  3. Use the threaded studs next to the Ethernet ports to mechanically secure the packs. The studs slip into a mounting bracket made for the particular style of the terminal board. It is important to position the bracket so that there is no right-angle force acting on the DC-37 pin connector between the terminal board and the pack. Only one adjustment should be necessary during the lifespan of the product.
  4. Depending on the setup of the machine, connect either one or two Ethernet wires. Either port will allow the pack to function. When using dual connections, it is customary to link ENET1 to the network connected to the R controller.
  5. Connect the connector on the side of the pack to a power source to power the battery. Because the I/O pack has an inherent soft-start feature that regulates current inrush on power application, it is not essential to turn off the power before plugging the cable in.
  6. If necessary, set up the I/O pack using the ToolboxST* program. See also the section on auto-reconfiguration.


Each Mark VIe Ethernet I/O pack or module shares a processing board. It has the following in it:

  • A quick processor with RAM and flash memory is number one.
  • Two plugs for entirely independent 10/100 Ethernet ports
  • Hardware reset and watchdog timer circuit
  • A sensor for internal temperature
  • LEDs that indicate the status
  • The capacity to read IDs on other boards and electronic identification
  • An input power connector with a current limiter and a gentle start
  • Local power supplies, which also include monitoring and sequencing

The I/O pack or module function-specific acquisition board is connected to the processor board. The soft-start circuit ramps up the voltage available on the processor board when input power is applied. The processor reset is turned off and the local power supply is turned on in order. After finishing self-test routines, the processor loads application code from flash memory that is particular to the I/O pack or module type. To verify that the application code, acquisition board, and terminal board are correctly matched, the application code reads the board ID information. When there is a good match, the processor makes an effort to start Ethernet connections by asking for a network address.

The dynamic host configuration protocol (DHCP), which is the industry standard, and the terminal board's unique identifier are both used in the address request. Following Ethernet startup, the CPU runs the application, programs the on-board logic, and permits the acquisition board to start working. The whole circuitry required to enable the I/O pack to function from one or two Ethernet inputs is contained in the processor application code. Both network pathways are constantly active when two Ethernet inputs are used. The I/O pack or module operation will not be hampered by a failure of either network, and the functioning network connection will reveal the failure. Compared to a traditional hot-backup system, where the second port is only used when the primary port fails to function, this configuration is more fault-tolerant. The processor's Ethernet ports automatically negotiate between half-duplex and full-duplex operation at speeds between 10 MB/s and 100 MB/s.

Flashing Pattern in Discrete Input


The second layer of signal conditioning and level shifting to connect the terminal board inputs to the control logic is provided by the discrete input acquisition board. On the terminal board, there is initial signal conditioning available. The comparator in the discrete input acquisition input circuit has a configurable threshold. A power supply isolated from the mains and an optocoupler isolate each input from the control logic. The inputs are connected to one another. The twenty-four inputs each have hysteresis, filtering, and a yellow status LED that flashes when an input is selected. When the input is lost, the LED will be off.


Variable Threshold


The contact wetting voltage input terminal serves as the source for the input threshold. This voltage is scaled in the majority of applications to offer an input threshold of 50%. To avoid an uncertain state in the case that the contact wetting voltage falls to zero, this threshold is clamped at 13 percent. The under-voltage detector notifies the control when the contact wetting voltage falls below 40% of the nominal voltage. There is a particular test mode available to force the control pack inputs. The threshold is pulsed high and low every four seconds to test the optocoupler's responsiveness. Inputs that don't reply are alarming.


Power management is a feature of the 28 V input circuit in the I/O pack. When applying power, the management function offers a gentle start to regulate the current inrush. A quick current limit function is provided by the circuit when power is applied to stop a pack or terminal board failure from spreading back into the 28 V power supply. The green PWR LED indicator will light up when there is power and everything is operating as it should. PWR LED will not light up again after the current limit function has been activated until the issue has been fixed.


  • The discrete input terminal board is directly connected to the I/O pack by a DC-37 pin connector on the underside. The 24 input signals, ID signal, relay coil power, and feedback multiplex command are all included on the connector.
  • The main system interface is an RJ45 Ethernet connector labeled ENET1 on the side of the pack.
  • The redundant or secondary system interface is a second RJ45 Ethernet connector on the side of the pack with the name ENET2.
  • The pack and terminal board are powered by 28 V dc through a 3-pin power connector on the side of the pack.

WOC has the largest stock of Speedtronic Mark VIe control spares. We can repair your faulty boards. WORLD OF CONTROLS can also supply unused and rebuilt backed up with a warranty. Our team of experts is available round the clock to support your OEM needs. Our team of experts at WOC is happy to assist you with any of your automation requirements. For pricing and availability on any parts and repairs, kindly get in touch with our team by phone or email.


What is IS220PDIAH1A?

The IS220PDIAH1A is an I/O pack in the Mark VIe series.

Which software is commonly used for the Mark VIe control system?

ToolboxST is used as the common software platform for programming, configuring I/O, trending, and analyzing diagnostics for Mark VIe and related controls.

How to obtain IS220PDIAH1A?

WOC can supply UNUSED and REBUILT IS220PDIAH1A backed up with a warranty.