HEIDENHAIN iTNC 530 HSCI Technical Manual page 1625

S → S,
Double changing
arm, M4540 = 1 or
MP7481.x, bit x = 1
July 2013
First the pocket number and tool number of the new tool are transferred.
Acknowledge with M4093.

Then the pocket tool number of the old tool and the tool number zero are
transferred.
Zero means clear the spindle!
8.15 Tool changer
1625