On Sat, 2008-04-26 at 09:45 -0400, Dave Keeton wrote:
> Chris,
>
> I have the baud rate set correctly......and the port.....what
> about stop bits and parity for the serial port? I can change it in my device
> but I am not sure what classic ladder is looking for......I have it hooked
> up with some input bits being triggered and I get nothing from/to
> classicladder.
The Modbus RTU standard indicates:
"
Bits per Byte: 1 start bit
8 data bits, least significant bit sent first
1 bit for parity completion
1 stop bit
Even parity is required, other modes ( odd parity, no parity ) may also
be used. In order to ensure a maximum compatibility with
other products, it is recommended to support also No parity mode. The
default parity mode must be even parity.
Remark : the use of no parity requires 2 stop bits.
"
For more see:
http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
Section 2.5.1
Good luck.
--
Kirk Wallace (California, USA
http://www.wallacecompany.com/machine_shop/
Hardinge HNC/EMC CNC lathe,
Bridgeport mill conversion, doing XY now,
Zubal lathe conversion pending
Craftsman AA 109 restoration
Shizuoka ST-N/EMC CNC)
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