Mega 2560 + 3 Tb6600 + Grbl, confusing Enable Pin. please help

Hi all pro,

I am a new comer in CNC. Pls help me with this issue

I am trying to connect 3pcs of TB6600 to 1 Mega 2560 as photo and using the GRBL firmware. (1.1)

https://images.app.goo.gl/p37FCyh5YAFbFtjV6
(sorry that I am using phone, I cant change photo to jpg or gif to upload it)

The confuse is that there is only 1 Stepper EN pin in the diagram and only 1 stepper En Pin is defined in the grbl code as followed (cpu_map.h)

#define STEPPER_DISABLE_BIT 7 // Mega2560 Digital pin 13.

Do I just ignore other 2 EN Pin of 2 remaining TB6600?

Thanks

Anybody there?