Red Lion C48T - Manual (Page 31)

Note: Command identifiers other than those listed should NOT be transmitted.
Otherwise, undefined or unpredictable operation could result.
The command string is constructed by using a command, a value identifier,
a data value if required, and the command terminator(*). The Data value need
not contain the decimal point(s) since they are fixed within the C48T, based on
the timer range programmed at the front panel. The unit will accept the decimal
point(s), however, it does not interpret them in any way. Leading zeros can be
eliminated, but all trailing zeros must be present.
Example: If a Preset of 1.000 is to be sent, the data value can be transmitted as
1.000 or 1000. If a “1” is transmitted, the Preset will be changed to 0.001.
The Address command is used to allow a command to be directed to a
specific unit on the Serial Communications Line. When the unit address is zero,
transmission of the Address command is not required. This is done for
applications that do not require more than one unit. For applications that require
several units, it is recommended that each unit on the line be given a specific
non-zero address. If they are given the same address, a command such as the
Transmit Value Command, will cause all of the units to respond simultaneously,
resulting in a communication collision. All units in a multiple unit application
should be given an address other than zero. If a unit has an address of zero, it
will attempt to process any transmissions from the other units as commands.
These transmissions fill up the receive buffer of the unit with an address of zero,
which may produce unpredictable results.
In a multiple unit configuration, an asterisk (2AH) must be sent to clear the
input buffer of all units on the line after a transmit value or print request
command is sent to a specific unit on the line. The C48T will require a
maximum of 50 msec to process the asterisk (*).
The command string is constructed in a specific logical sequence. The C48T
will not accept command strings that do not follow this sequence. Only one
operation can be performed per command string. Below is the procedure to be
used when constructing a command string.
1. The first two to three characters of the command string must consist of the
Address Command (N) and the address number of the unit (1 thru 99). If the
C48T address is zero, the address command and number need NOT be sent.
2. The next character in the command string is the actual command that the unit
is to perform (P, R, S, T, or V).
3. A Value Identifier is next if it pertains to the command. The command P
(print) does not require a Value Identifier.
4. The numerical data will be next in the command string if the Change Value
command (V) is used.
5. All command strings must be terminated with an asterisk * (2AH). This
character indicates to the C48T that the command string is complete.
Below are some typical examples of properly constructed command strings.
Examples:
1. Change Preset 1 Value to 123.4 on the C48T with an address of 2.
COMMAND STRING: N2VA1234*
2. Transmit the Timer Value of the C48T unit with an address of 3.
COMMAND STRING: N3TE*
3. Reset Output 1 of the C48T unit with an address of 0.
COMMAND STRING: R1*
If illegal commands or characters are sent to the C48T, the unit will respond
by transmitting an error character “E” (45H), in which case the string must be
re-transmitted.
When writing application programs in Basic, the transmission of spaces or
carriage return and line feed should be inhibited by using the semicolon
delimiter with the “PRINT” statement. The C48T will not accept a carriage
return or line feed as valid characters. See Terminal Emulation Program, page
27, for a listing of an IBM
® PC Basic terminal emulation program.
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A (41H) Preset 1 P1
B (42H) Preset 2 P2
E (45H) Timer TMR
1 (31H) Output 1 N/A
2 (32H) Output 2 N/A
VALUE IDENTIFIERS MNEMONIC
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