Configure the Omron Host Link Connector
Connect SIA Connect to an Omron PLC through Host Link serial communication, configure memory items, and troubleshoot communication errors.
The Omron Host Link Connector connects SIA Connect to Omron PLCs that support the Host Link serial protocol. It can read and write PLC memory through an RS-232 or RS-422/RS-485 serial connection.
This guide explains how to configure the serial connection, create items for PLC memory addresses, select the correct data type, verify communication, and resolve common errors.
Writing to PLC memory can change machine behavior. Confirm the destination address, data type, value range, and PLC operating state before enabling writes.
Supported equipment
The Connector is intended for Omron PLCs that support Host Link communication. The current Connector source identifies the following tested models:
- Omron CQM1H
- Omron CP1L
Other Omron controllers can work when they support the same Host Link commands, memory areas, and serial settings. Check the programming manual for the specific PLC and communication unit.
Before you begin
Prepare the following information:
- The PLC Host Link unit number
- The serial interface connected to SIA Connect
- The baud rate, parity, data bits, and stop bits configured on the PLC
- The PLC memory areas and addresses to read or write
- The data type and size stored at each address
Also confirm that:
- The Omron Host Link Connector is installed and enabled.
- The serial wiring and signal standard match the PLC interface.
- The PLC and any serial adapter use compatible RS-232 or RS-422/RS-485 electrical connections.
- No other Connector instance is using the same serial interface at the same time.
- The PLC serial port does not require RTS/CTS or XON/XOFF flow control. The Connector disables hardware and software flow control.
Create an Omron Host Link instance
- Sign in to the Edge Portal.
- Open Workspace > Instances.
- Select Add instance.
- Select the Omron Host Link Connector.
- Enter a descriptive instance name.
- Enter the PLC Host Link unit number in Address.
- Configure the Connector parameters described below.
- Select Create.
Instance parameters
| Parameter | Required | Default | Accepted values | Description |
|---|---|---|---|---|
| Address | Yes | 00 |
PLC Host Link unit number | Identifies the PLC or Host Link unit. The command formats numeric values with at least two digits. Omron Host Link networks commonly use unit numbers 00 to 31. Use the value configured on the PLC. |
| Timeout | Yes |
10000 ms |
Positive whole number | Maximum time to wait for a serial response. The current implementation applies the timeout in whole seconds, so use a multiple of 1000. |
| Serial port | Yes | None | Available serial interfaces | Select the physical or USB serial interface connected to the PLC. |
| Baudrate | Yes | 9600 |
1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, or 230400
|
Serial transmission speed. It must match the PLC. See the current limitation for 230400. |
| Parity | Yes | Even | None, Even, or Odd | Parity used for each serial character. |
| Data bits | Yes | 7 |
5, 6, 7, or 8
|
Number of data bits in each serial character. |
| Stop bits | Yes | 2 |
1 or 2
|
Number of stop bits at the end of each serial character. |
The standard Omron Host Link serial configuration is commonly 9600 baud, 7 data bits, even parity, and 2 stop bits, also written as 9600 7E2. The PLC configuration takes precedence.
Add an item
- Open the Omron Host Link instance.
- Open the Items section.
- Select Add item.
- Enter a descriptive item name.
- Select the required Read write setting.
- Enter the PLC memory location in Address.
- Select the matching Data type.
- Set the read interval and any required logging or processing options.
- Select Create.
Use Read only for values that SIA Connect only reads. Use Read and Write or Write only only when the PLC memory area permits writes and the application requires them.
Item parameters
| Parameter | Required | Default | Description |
|---|---|---|---|
| Address | Yes | None | PLC memory area and starting word. Add a bit position for Bool, for example D100.3. |
| Data type | Yes | None | Controls how many 16-bit words are read or written and how the response is converted. |
Address memory areas
Enter the memory-area name directly before the word number. Leading zeroes in the word number are optional.
| Entered memory area | Host Link area code used by the Connector |
|---|---|
R, S, IR, or SR
|
R |
H or HR
|
H |
A or AR
|
A |
L or LR
|
L |
T or TC
|
T |
D or DM
|
D |
X or FX
|
X |
CI or CIO
|
I |
Examples:
-
D100reads or writes from DM word 100. -
DM0100refers to the same starting word. -
H22accesses holding-relay word 22. -
D100.3accesses bit 3 of DM word 100.
The word number must be between 0 and 9999. Bit positions must be between 0 and 15. Available memory areas and write permissions depend on the PLC model and operating mode.
Select a data type
Omron PLC memory is organized as 16-bit words. Multiword data types automatically read or write consecutive words starting at the configured address.
| Data type | Size | Value format |
|---|---|---|
| Bool | One bit in one word |
0 or 1. Use an address with a bit position. |
| Int16 | 1 word | Signed 16-bit integer |
| Int32 | 2 words | Signed 32-bit integer |
| Int64 | 4 words | Signed 64-bit integer |
| Word | 1 word | Unsigned 16-bit word value |
| Double word | 2 words | Unsigned 32-bit word value |
| Quad word | 4 words | Unsigned 64-bit word value |
| BCD 16 | 1 word | Up to 4 binary-coded decimal digits |
| BCD 32 | 2 words | Up to 8 binary-coded decimal digits |
| BCD 64 | 4 words | Up to 16 binary-coded decimal digits |
| Real | 2 words | 32-bit IEEE 754 floating-point value |
| Long Real | 4 words | 64-bit IEEE 754 floating-point value |
Select the type that matches the PLC program. An incorrect size can read adjacent memory words or produce an invalid value.
Understand bit writes
Host Link writes complete words rather than individual bits. When writing a Bool item, the Connector:
- Reads the complete 16-bit word.
- Changes the selected bit.
- Writes the complete word back to the PLC.
Another controller or application could change a different bit between the read and write operations. Avoid concurrent writes to the same word when this could affect the process.
Verify communication
- Enable the instance and at least one read-only test item.
- Confirm that the instance and item do not show an active error.
- Compare the current item value with the same address in the Omron programming software.
- Confirm that the value changes when the PLC memory changes.
- If writing is required, place the equipment in a safe state and write a controlled test value.
- Read the address again and confirm that the PLC accepted the value.
The item shows the correctly formatted value from the selected PLC memory address. A permitted test write is reflected in the PLC.
Troubleshoot the Omron Host Link Connector
| Message or symptom | Likely cause | Action |
|---|---|---|
| Error initializing serial port | The selected interface is unavailable, invalid, disconnected, or already in use. | Check the cable and adapter, select the correct serial port, and make sure another instance or application is not using it. |
| Timeout or Timeout reading | No complete response arrived before the timeout. | Check power, wiring, signal standard, unit number, and all serial settings. Increase the timeout if the PLC responds slowly. |
| System: No such memory address or System: Address is invalid | The memory-area name, word number, or bit syntax is invalid. | Use a supported area followed by a word number. Use .0 to .15 only for Bool items. |
| System: Data format error or System: Data provided invalid | The written value does not match the selected data type. | Check the item type and send a compatible integer, floating-point, BCD, or Boolean value. |
| System: Type size exceeded | The value cannot be represented by the selected data type. | Correct the value or select the data type used by the PLC program. |
| System: Invalid boolean value | A Bool write used a value other than 0 or 1. |
Write 0 for false or 1 for true. |
| PLC: Parity error | The parity setting or received serial data is incorrect. | Match the PLC parity and inspect the cable, grounding, and serial adapter. |
| PLC: Framing error stop bits not detected | The baud rate, data bits, parity, or stop bits do not match. | Compare all serial settings with the PLC or Host Link unit. |
| PLC: Overrun the next command was received too soon | Requests are reaching the PLC faster than it can process them. | Increase the item read interval and reduce competing serial traffic. |
| PLC: FCS error | The frame checksum is incorrect or serial data was corrupted. | Check serial settings, wiring quality, shielding, grounding, and electrical noise. |
| PLC: An incorrect data area designation was made for READ or WRITE | The selected memory area or operation is not supported by the PLC. | Check the model-specific memory map and whether the area can be read or written in the current mode. |
| PLC: The specified Memory Unit is write-protected | The requested address cannot be written. | Use a writable area or change the PLC protection only when permitted by the application. |
The value is incorrect but no error is shown
- Confirm that the item starts at the correct word.
- Confirm that the selected type uses the same number of words as the PLC value.
- Check whether the PLC program stores a signed integer, unsigned word, BCD value, or IEEE 754 floating-point value.
- Compare the raw words with the Omron programming software.
A write is rejected because of the PLC mode
The PLC can reject commands in RUN, MONITOR, PROGRAM, DEBUG, or LOCAL mode depending on the command and controller. The returned PLC error describes the mode that blocked execution. Change the PLC mode only when it is safe and permitted.