is PAN4555 capable of transmitting/recieving RS485?

[darin]

Basically that is the question...  Is the PAN4555 capable of transmitting/recieving RS485? 

If it is capable, what does it take to set that up (for a complete n00b)?

So far I have the evaluation board kit, usb BDM connector, and Codewarrior for HCS08 (that came with the BDM connector).  I believe that it is the MC1321x or MC9S08GT60 but cannot figure out which package it is.

I've been struggling to understand this controller so any insight would be very appriciated.

-Darin

[Mads]

darin,

you can find the datasheet and reference manual for the MC1321x on this URL:

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC13213&nodeId=01J4Fs25657103

Br,

MADS

[darin]

Thanks Mads for the response but I think made the question to general.  I'm trying to figure out if any of the IO's from the MCU on the pan4555 can be programmed to directly output a RS-485 signal..  Or can it really only put out a TTL signal?

[peg]

Hi darin,
The actual PAN4555 module simply brings out both SCI ports from the internal MC13213 at their raw data levels (3volt ish).
The evaluation board allows either of these to be converted to RS-232 levels and brought out on a DB-9.
There is space for a second circuit like this but it is not populated and is still RS-232 anyway.
What you could do is make your own adapter for RS-485 that plugs into one of the spare pin headers.

[darin]

Thank you all for the replies.  I understand why now it is not possible to have a direct output of RS485 from the MCU.  I will start looking for a RS485 Interface chip to convert the signal.  Thanks again!

[bigmac]

Hello Darin,

I am not familiar with the hardware details of the PAN4555 board, but perhaps this question can be answered more generally.

Both RS232 and RS485 communications make use of an SCI module within the MCU.  Since the pins of the MCU approximate TTL switching levels, a separate interface device will always be required to generate the required drive levels, and accommodate the voltage levels associated with each type of communications interface.

RS232 communications would normally operate in "full-duplex" mode, where transmission and reception may simultaneously occur.  Two separate lines handle transmit data and receive data.  By contrast, RS485 communications will usually operate in "half-duplex" mode, where transmission and reception cannot occur simultaneously, since all communications will be handled by a single balanced pair connected to the interface device.  Therefore, RS485 will require an additional control signal from the MCU, to determine when transmit mode is selected.  The control of this pin will require additional code.

It is possible that the PAN4555 may already incorporate an RS232 interface.  If so, there are two possibilities -

1. If you wish to use the same SCI module as is currently used for RS232, the existing RS232 interface device will need to be disabled, in particular the external signal applied to the RX pin of the MCU.  You will also need external access to both TX and RX pins, and the additional control pin, to connect to an external RS485 interface device.
2. An alternative would be to use the other SCI module within the device, provided you have external access to its pins.

Regards,

Mac