MC2340 ETC1 [List of Unclassifed Manufacturers], MC2340 Datasheet - Page 38

• Manufacturer Part Number: MC2340
• Description: Technical Specifications for Brushless Servo Motion Control
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

6 Application Notes
6.1
Design Tips
The following are recommendations for the design of circuits that utilize a PMD Motion Processor.
Serial Interface
The serial interface is a convenient interface that can be used before host software has been written
to communicate through the parallel interface. It is recommended that even if the serial interface is
not utilized as a standard communication interface, that the serial receive and transmit signals are
brought to test points so that they may be connected during initial board configuration/debugging.
This is especially important during the prototype phase. The serial receive line should include a pull-
up resistor to avoid spurious interrupts when it is not connected to a transceiver.
If the serial configuration decode logic is not implemented (see section 6.3) and the serial interface
may be used for debugging as mentioned above, the CP data bus should be tied high. This places the
serial interface in a default configuration of 9600,n,8,1 after power on or reset.
Controlling PWM output during reset
When the motion processor is in a reset state (when the reset line is held low) or immediately after a
power on, the PWM outputs can be in an unknown state, causing undesirable motor movement. It is
recommended that the enable line of any motor amplifier be held in a disabled state by the host
processor or some logic circuitry until communication to the motion processor is established. This
can be in the form of a delay circuit on the amplifier enable line after power up, or the enable line can
be ANDed with the CP reset line.
Reducing noise and power consumption
To reduce the emission of electrical noise and reduce power consumption (caused by floating inputs),
all unused input signals can be tied through a resistor to Vcc or directly to GND. The following CP
pins can be tied if not used: 45, 48, 68-70, 73, 90, 91, 101, 102, 105, 107-109, 78-81.
Parallel word encoder input
When using parallel word input for motor position, it is useful to also decode this information into
the User I/O space. This allows the current input value to be read using the chip instruction ReadIO
for diagnostic purposes.
Using a non standard system clock frequency
It is often desirable to share a common clock among several components in a design. In the case of
the PMD Motion Processors it is possible to use a clock below the standard value of 40MHz. In this
case all system frequencies will be reduced as a fraction of the input clock verses the standard
40MHz clock. The list below shows the affected system parameters:-
•
Serial baud rate
MC2300 Technical Specifications
38