Ruth Hendrix

Connecting hardware to the monitor mode communication pin

Discussion created by Ruth Hendrix Employee on Jan 19, 2006
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Posted: Wed Nov 24, 2004 2:38 am

Hi there

I am fairly new to micros and very new to the HC08.

So, is it possible to connect I/O hardware to the communication pin of a HC08 GP32 (from memory I/O A0)?

Or, do I have to physically disconnect the hardware?

At the moment, I would like to use an LCD screen in 8 bit mode, but, cannot leave all the 8 wires connected for simulation. I am also intending to use most other I/Os.

Thanks for any help provided.

Posted: Wed Nov 24, 2004 1:11 pm      

I'm not absolutely certain what you are trying to achieve here, but it sounds like you are asking if one of the comms pins on the 08 can also be used as standard I/O.
If that is the question then the answer is yes. For example the SCI transmit pin on Port E0 can alternatively be used as a simple output or input pin. Obviously you can't use it as a transmit and I/O pin at the same time.

Posted: Wed Nov 24, 2004 9:39 pm    

Thanks for the reply

The problem arose when I had the LCD connected to all 8 bits of PORTA.

I just could not even get into monitor mode with bit 0 connected. Disconnect that one bit, and monitor mode was fine and the LCD worked (although with wrong data on bit 0).

I suppose that in this particular case, I would like to be able to use the LCD in 8 bit mode at all times, with bit 0 giving incorrect data to the LCD when in monitor mode.

I guess a hardware buffer between the monitor mode connection and the LCD connection to prevent a signal from the LCD travelling back up the line to the monitor mode connection may work, but, what components?

This is no longer important, but, I am curious none the less.

Have fun

Posted: Wed Nov 24, 2004 10:17 pm    

Hi Guys,

I'm thinking that in your soft you can make a difference between being in User mode or Monitor mode, you could switch the A0 as input in Monitor mode and not worry about it interfering with the communication.


Posted: Wed Mar 30, 2005 5:03 am    

 am using Port A for LEDs and 7 segments displays without any problem and bit 0 is always connected to the MAX232.

I never disconnect anything to program it. I can even see/monitor the data sent or received while programming with the LED.

But I admit I use a 74HC573 to drive the LEDs.

Oh, btw, the only time it can be a problem is in debug mode because you loose control of the uC when you output something on PA0.