Acknowledgments --------------- The **modbus** package is based on the `modtcp and plctcp packages `__ written by Rolf Keitel from Triumf. The **modtcp** package was originally converted to Linux by Ivan So from NSLS. **modbus** was extensively re-written for conversion to EPICS 3.14 and to use the EPICS asyn module. It now contains little of the original **modtcp** code, but retains much of the original architecture.