How to configure and programming to write bool values to siemens plc s7.300 via modbu

Hi Sir,

I am using S7-300/400. I am usually using FC 03 and FC04 to transfer (R/W) bool values by moving them DBs. However i want to R/W bool values directly to plc ( slave) from master yoko dcs. I configured FC 01 and FC02 in slave slide ( write to Memory M) and used function A0 and A1 in dcs side. I cant write directly to M ( from M300.0 with 10 byeltes).
Thank you very much for yours help.

Literature.

To emulate a modbus server on a Siemens s7300/400 plc you need modbus libary from Siemens and that licence is expensive.
When the S7 is connected over ethernet to Yoko dcs using cp343/443 module on s7 site then this link could be helpfull.

https://www.sps-forum.de/simatic/14182-modbus-tcp-funktionbausteine-step-7-a-3.html
Used it for modbus tcp communication between S7 plc with CP443 and CTI plc acting as modbus client.

Kind regards
Henny