Matrix MI3932 MIAC AllCode, Руководство по началу работы, Страница: 25 / 29

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Transistor Outputs
Using PWM
MIAC AllCode
Instructional Guide
There are four transistor outputs on the MIAC but there are actually six control lines from the internal microcontroller.
By default when using the transistor outputs as simple on/off controllers the extra two enables signals can be ignored.
When driving things like DC motors it can be useful to use PWM on the enable signals to set the speed of the motor.
The transistor outputs can then be used to set the direction of the motor.
Two DC motors can be driven from the MIAC in full bridge mode.
For complete control all six outputs can be used with pulse width modulated (PWM) output and are numbered as follows.

Channel 0 = Enable0 (AB)

Channel 1 = Transistor Output A

Channel 2 = Transistor Output B

Channel 3 = Transistor Output C

Channel 4 = Transistor Output D

Channel 5 = Enable1 (CD)
Here is a block diagram of the internal workings of the transistor outputs.
The states of the control signals have the following effect on the transistor outputs.
For simplicity the Enable0 and A/B outputs share a PWM timer, prescaler and period though the duty can vary for each output.
Enable1 and C/D outputs also share their own unique PWM timer, prescaler and period.
PWM duties are 16-bit by default with the range of 0 to 65535.
The overall duty can be altered by changing the PWM period.
Enable0 A B Output
Low Don’t Care Don’t Care Coast
High Low Low Brake
High Low High Forwards
High High Low Backwards
High High High Brake