MC68336/376
TIME PROCESSOR UNIT
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
11-12
center aligned mode uses 2n + 1 channels. Center aligned mode allows a user-defined
“dead time” to be specified so that two PWMs can be used to drive an H-bridge without
destructive current spikes. This feature is important for motor control applications.
Refer to TPU programming note Multichannel Pulse-Width Modulation (MCPWM)
TPU Function (TPUPN05/D) for more information.
11.5.6 Fast Quadrature Decode (FQD)
FQD is a position feedback function for motor control. It decodes the two signals from
a slotted encoder to provide the CPU32 with a 16-bit free running position counter.
FQD incorporates a “speed switch” which disables one of the channels at high speed,
allowing faster signals to be decoded. A time stamp is provided on every counter
update to allow position interpolation and better velocity determination at low speed or
when low resolution encoders are used. The third index channel provided by some
encoders is handled by the NITC function.
Refer to TPU programming note Fast Quadrature Decode (FQD) TPU Function
(TPUPN02/D) for more information.
11.5.7 Universal Asynchronous Receiver/Transmitter (UART)
The UART function uses one or two TPU channels to provide asynchronous serial
communication. Data word length is programmable from one to 14 bits. The function
supports detection or generation of even, odd, and no parity. Baud rate is freely pro-
grammable and can be higher than 100 Kbaud. Eight bidirectional UART channels
running in excess of 9600 baud can be implemented.
Refer to TPU programming note Universal Asynchronous Receiver/Transmitter
(UART) TPU Function (TPUPN07/D) for more information.
11.5.8 Brushless Motor Commutation (COMM)
This function generates the phase commutation signals for a variety of brushless
motors, including three-phase brushless DC motors. It derives the commutation state
directly from the position decoded in FQD, thus eliminating the need for hall effect
sensors.
The state sequence is implemented as a user-configurable state machine, thus
providing a flexible approach with other general applications. An offset parameter is
provided to allow all the switching angles to be advanced or retarded on the fly by the
CPU32. This feature is useful for torque maintenance at high speeds.
Refer to TPU programming note Brushless Motor Commutation (COMM) TPU
Function (TPUPN09/D) for more information.
11.5.9 Frequency Measurement (FQM)
FQM counts the number of input pulses to a TPU channel during a user-defined win-
dow period. The function has single shot and continuous modes. No pulses are lost
between sample windows in continuous mode. The user selects whether to detect