Modicon Controllers
The Modbus RTU Communications option supports reads from the following memory types on Modicon controllers:
| Coils | 0xxxx or 0xxxxx |
| Inputs | 1xxxx or 1xxxxx |
| Input Registers | 3xxxx or 3xxxxx |
| Holding Registers | 4xxxx or 4xxxxx |
| General Reference | 6yxxxx or 6yxxxxx |
| Holding Registers as Double Precision | D4xxxx or D4xxxxx |
The Modbus RTU Communications option supports writes to the following memory types on Modicon controllers:
| Coils | 0xxxx or 0xxxxx |
| Holding Registers | 4xxxx or 4xxxxx |
| General Reference | 6yxxxx or 6yxxxxx |
| Holding Registers as Double Precision | D4xxxx or D4xxxxx |
CAUTION: When writing to Coils (0xxxx or 0xxxxx), memory protect and coil disable are overwritten.
On Modicon controllers, coils that are not programmed in the controller logic program are not automatically cleared on power up. This means that if a coil is set to 1, the output will remain HOT until explicitly set to 0.
Writing to Holding Registers overrides the controller memory protect.