Product specifications

R01AN0168ED0101 Rev. 01.01 46

Application Note

Chapter 7 Performing Zero Point Detection

7.3.1 Using Direct I/O Control

When performing ZPD, it is often mandatory to perform special settings on the

port outputs to the stepper motors, like creating short-cuts, keeping the

measured end of a coil open, or driving current through the motor permanently.

To allow to do these kind of things, the

Direct I/O Control function is available.

It is activated by the flags

IHEn and IVEn.

If these are set, any PWM output to the motor

n is disabled for these coils, and

instead, the motor ports are driven by the codes of

IHDn and IVDn directly.

Also,

recirculation is disabled, if Direct I/O Control is active.

Note However, even if Direct I/O Control is active, the break-before-make safety

system of ISM still remains active. Therefore, it is not possible to destroy

outputs by wrong codes, i.e., by trying to create power shortcuts.

Figure 7-9 Virtual Transistors for Direct I/O Control

The control codes for Direct I/O Control are referring to “virtual transistors”,

which are forming a H-FET bridge, where the motor coil is connected to.

Every code of

IHDn and IVDn is a bit-field of the activation of the transistors T1

to T4, where “1” means an activated transistor.

Examples:

–IHD = 0110B: Full powered coil from M to P (reverse current),

(SMn2 to SMn1, or SMn4 to SMn3).

–

IHD = 0101B: Coil is short-cut via ground level.

–

IHD = 0011B: This is an illegal code. The safety system of ISM will 

refuse to activate neither T3, nor T4.

VCC of SM

VSS of SM

H-FET Bridge