by lots of test at finally I achieved the object that communication between mach3 and PLC modbus,thank u Scott so much!
but an other question:
1.by inputting the Brain Editor£¨Modbus input with "Serial Non-Plugin Enabled"£©
2.at the box of¡°1 Input Lobe¡±,I choose the ¡°comare Immediate¡±¡°Equal To 1¡±
3.which output is Botton¡°303- MPG1 MODE:0¡±
at the stakeout¡°BrainView¡±I can see the sentence of the programme is availability.
but when I press the button of the definiens input,mach3 always back to the picture,for example,in the ¡°Diagnostics¡±,press the button which has been defined, the mach3 screen will back to the ¡°Program Run¡±picture.
Why??

A few things:

1). Use the "Serial Plugin Modbus" (NOT the non-plugin)
2). The characters of your keyboard do NOT translate well, so Put a copy of your "Brains" that you are using on this site, they will upload nativley as an attachement.
3). Chances are, you are using the wrong OEM code in your termination button. Or you custom button on the diagnostic screen has a "DoOEMButton(1) in it that is jumping you to the main page.

Note: The Modes of the MPG are function states, I.e. step, continous, MPG control
If you want to watch the "Brain view" at the same time as your pushing buttons on the Mach Page, then you will have to "Resize Mach" so that you can watch the brain and Mach with out them being one on top of the other. (I would HIGHLY recommend a second Monitor, that way you can have full size Mach on one screen, and your Brain view on the other.

scott