MC68332: problems with serial communication

joel at joel at
Sat Dec 9 03:48:38 UTC 2000

I saw this on UseNet and wondered if anyone had any advice to offer.

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Subject: MC68332: problems with serial communication
From: Tobias Kolb <kolb at>
Date: 2000/12/05
Newsgroups: comp.sys.m68k

I´m developing a PWM-converter for a small induction-machine using the
nf300-board from under
RTEMS 4.0 and Linux.
We use a modified board support package from the efi332 project
The control algorithm is basically the same (Assembler-Code ported to C)
as described in Motorolas application note AN1310
"Using the MC68332 Microcontroller for AC Induction Motor Control".
In short form:
TPU-channel 5 is generating a square wave.
TPU-channel 6 is configured as input transition counter (ITC) and starts
an interrupt-routine on
TPU-channel 7 every 225us.
The intterupt routine is looking up a sinus from a lookup-table to
modulate the output TPU-channels 1,2 and 3.
TPU-channel 0 defines the linked TPU-channels 1,2,3 wich generate the
three-phase output PWM for the inverter control logic.

Now my problem is, that when the program on the controller is started
via keyboard and serial communication from the "minicom" terminal in the
Linux-box, the controller doesn´t accept any keyboard strikes from the
Linux-box anymore, for instance a brake command for the induction
If the order of the invoked TPU-channels is changed, for instance
TPU-channel 0 defines the linked TPU-channels 1,3 and 5 as PWM-output
former TPU-channel 5 is shifted to channel 7,
former TPU-channel 6 is shifted to channel 8 and
former TPU-channel 7 is shifted to channel 9,
the program accepts keyboard strikes via the serial communication but
doesn´t do the modulation of the output-channels properly anymore.

The "user-code" doesn´t deal with the serial communication, this is
defined in the board-support-package.
Reducing the intterupt frequency didn´t change anything.
I´m not very deep into embedded developing so I would greatly appreciate
any hints from the group!
Thanks in advance,

greetings from Stuttgart, Germany,

Tobias Kolb

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