PRO-TC-MAN-17V01 (0802)
Copyright © 2017 Define Instruments
24
A
APPENDIX A - SERIAL MODES
A.1 - Custom ASCII mode
Custom ASCII is a simple, custom protocol that allows connection to various PC con-
figuration tools. ('Custom ASCII' differs from the 'Modbus (ASCII)' protocol used by
some devices.) Custom ASCII command strings must be constructed in this order:
<Start> <Controller Address> <Read/Write Command> <Register Address>
<Separator Character> <Data Value> <Message Terminator>
Start -
Use '
S
' for the start character of a command string (not case sensitive). This
must be the first character in the string.
Controller Address -
Use an ASCII number from '
1
' to '
255
' for the controller address.
If the character following the start character is not an ASCII number, then ad-
dress '
0
' is assumed. All controllers respond to address '
0
'.
Read/Write Command -
Use ASCII '
R
' for read, '
U
' for unformatted read, or '
W
' for
write (not case sensitive). Any other character aborts the operation.
In Custom ASCII mode, data is normally read as formatted data (which includes decimals and
any text characters that may be selected to show units). However it is also possible to read un-
formatted data by using a 'U' in the read command. There is no unformatted write command,
as when writing to fixed point registers, any decimal point and text characters are ignored.
Register Address -
The register address for the read/write operation will be an ASCII
number from '
1
' to '
65535
'. This character must be specified for a write com-
mand, but may be omitted for a read command, (in which case the controller
will respond with the data value currently on the display).
Separator Character -
The separator character can be either a space or a comma,
and is used to separate the register address from the data value.
Data Value -
Must be an ASCII number. The absolute limits for this number are
–
1000000
to
+
1000000
, but note that not all registers will accept this range.
Message Terminator -
This is the last character, and must be either a '
$
' (dollar) or
an '
*
' (asterisk). Neither of these characters should be used elsewhere in the
