12.1.1 TPIC0108 Logic for DC Motors

The logic to control the two lines of the TPIC0108 uses the following truth table:

$\overline{\mathrm{PWM}}$	DIR	$\overline{\mathrm{BRK}}$	IN1	IN2	comments
1	?	?	0	0	quiescent hi-Z (off)
0	?	0	1	1	brake
0	1	1	0	1	one way
0	0	1	1	0	the other way

The equation for IN1 is as follows:

$$\mathrm{IN1} = \overline{\overline{\mathrm{PWM}}} \times ... ...rline{\overline{\mathrm{PWM}}} \times \overline{\mathrm{DIR}}$$ (12.1)

Whereas the equation for IN2 is as follows:

$$\mathrm{IN1} = \overline{\overline{\mathrm{PWM}}} \times \overlin... ...verline{\mathrm{BRK}}} + \overline{\overline{\mathrm{PWM}}} \times \mathrm{DIR}$$ (12.2)

This allows a PWM line be used for each channel. Note that the PWM signal and the BRK signal are both active-low so that the default state can be pulled-up when the controller is in reset state.

This plan uses 3 input channels per H-bridge for maximum flexibility. Since this is often only useful for DC motors, we only need to use 6 lines from the MCU to control two DC motors.