From http://www.control.com/thread/1026153964

In its simplest form Memobus is Modbus and you can access much of the data that is in a Yaskawa controller using normal Modbus commands from just about any Modbus driver.

Manuals from Yakawa:

Modbus vs Memobus.pdf - Yaskawa

MEMOBUS/Modbus Communications

These extracts should be of interest:

· Bits (1 bit), Words (16 bits), and Long Words (32 bits), and Floating Point words (32 bits) take up the SAME address space (unlike straight Modbus).

Example:
MB000001=1 is same as MW00000=1 is same as ML00000=1. This means that

0XXXX coils, 1XXXX input relays, and 3XXXX input registers do not exist.

· Register numbers are to be mapped directly (no offset).

Example:

Memobus Modbus

MW00000 = 40001

MW00040 = 40041

I recommend you study the documents above along with the Modbus functions for the S7-1200 CPUs, and see if you can use these to communicate with the Yaskawa drives. Youc should also read the following thread from the forum, member prmius1points toa description of the Modbus commands for the S7-1200 PLC and a Step 7 v. 11 sample program he used to control a Yaskawa drive:
/tf/WW/en/Posts/52961

Hope this helps,
Daniel Chartier