Re: Help with Zilog180 ASCI on COM1
From: Jack Klein (jackklein_at_spamcop.net)
Date: 01/19/05
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Date: Tue, 18 Jan 2005 20:20:44 -0600
On Tue, 18 Jan 2005 15:34:26 -0500, Tosca Berisha <tberisha@uucp.gov>
wrote in comp.arch.embedded:
> Hi all,
>
> I got thrown into a project that has Zilog 180 onboard. I am trying to
> make this device communicate with PC using the famous 3 wire serial
> cable. But, I am having so many Overrun Error (OVRN) and Framing Error
> (FE) problems. Even at 300 baud at 2 stop bits. The processor is clocked
> with a 4.608 MHz Oscilator and I am using the ASCI Baud Rate Selection
> Table (on Z180 PDF) for choosing speeds.
>
> The hardware designer is not around anymore, and I can not get any other
> help. Line driver is ADM232LJN.
>
> Are there any know issues with communication with Z80 or Z180.
>
> Thanks,
> //Tosca
Verify the baud rate like this:
Set your serial port for some baud rate, such as 9600. Also set it to
transmit 8-bit bytes with no parity. Write a test program to run on
the board that does nothing but transmit the ASCII character 'U' (55
hex) continuously. Put a scope on the transmit pin, and you should
see a 50/50 duty cycle waveform. Measure the width of either the high
or low portion of the pulse. It should be 104.166 microseconds for
9600 baud.
Also check the voltage of the signals, it should range from less than
-3 volts for the low to greater than +3 volts for the high.
If either of those is not correct, fix it, either hardware or adjust
the value you are loading into the baud rate generator or other
control bit in the serial port.
If this is all correct, post again and include your source code for
the serial port driver code. Copy and paste the source code text into
the body of your message please, no attachments.
-- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ http://www.contrib.andrew.cmu.edu/~ajo/docs/FAQ-acllc.html
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