MC3PHAC Monolithic Intelligent Motor Controller, Rev. 2

28

Freescale Semiconductor

Operation

Command State Machine

When using the PC master software mode of operation, the command state machine governs behavior

of the device depending upon its current state, system parameters, any new commands received via

the communications link, and the prevailing conditions of the system. The command state diagram is in

Figure 18. It illustrates the sequence of commands which are necessary to bring the device from the reset

condition to running the motor in a steady state and depicts the permissible state transitions. The device

will remain within a given state unless the conditions shown for a transition are met.

Some commands only cause a temporary state change to occur. While they are being executed, the state

machine will automatically return to the state which existed prior to the command being received. For

example, the motor speed may be changed from within any state by using the WRITEVAR16 command

to write to the "Speed In" variable. This will cause the "Set Speed" state to be momentarily entered, the

"Speed In" variable will be updated and then the original state will be re-entered. This allows the motor

speed, acceleration or base frequency to be modified whether the motor is already accelerating,

decelerating, or in a steady state.

Each state is described here in more detail.

•

Reset — This state is entered when a device power-on reset (POR), pin reset, loss of crystal,

internally detected error, or reset command occurs from within any state. In this state, the device

is initialized and the PWM outputs are configured to high impedance. This state is then

automatically exited.

•

PWMHighZ — This state is entered from the reset state. This state is also re-entered after one and

only one of the PWM dead-time or polarity parameters have been initialized. In this state the PWM

outputs are configured to a high-impedance state as the device waits for both the PWM dead time

and polarity to be initialized.

•

SetDeadTime (write once) — This state is entered from the PWMHighZ state the first time that a

write to the PWM dead-time variable occurs. In this state, the PWM dead time is initialized and the

state is then automatically exited. This state cannot be re-entered, and hence the dead time cannot

be modified, unless the reset state is first re-entered.

•

SetPolarity (write once) — This state is entered from the PWMHighZ state the first time that the

PWM polarity command is received. In this state, the PWM polarity is initialized and the state is

then automatically exited. This state cannot be re-entered, and hence the polarity cannot be

modified, unless the reset state is first re-entered.

•

PWMOFF — This state is entered from the PWMHighZ state if both the PWM dead time and

polarity have been configured. In this state, the PWM is activated and all the PWM outputs are

driven off for the chosen polarity. The device then waits for the PWM base frequency, motor speed,

and acceleration to be initialized.

•

PWM0RPM — This state is entered from the PWMOFF state when the PWM base frequency,

motor speed, and acceleration have been initialized. This state can also be entered from the

FwdDecel or RevDecel states if a CmdStop command has been received, and the actual motor

speed has decelerated to 0 r.p.m. In this state, the PWM pins are driven to the off state for the

chosen polarity. The only exit of this state is to the PWMPump state, which occurs when a CmdFwd

or CmdRev command is received.