7-1
There are two (2) classes of operation associated with meter serial communications:
Point-to-point and Multipoint. (Refer to Section 10.13)
7.1 POINT-TO-POINT
No device address is included in the command or response message when operating
in this class. There are two (2) modes associated with this class; CONTINUOUS and
COMMAND.
7.1.1 CONTINUOUS MODE
For RS-232, the computer can direct the meter to repeatedly transmit the data and
status information in the format specified by the communications setup (which includes
a selectable parameter to space out the transmissions for data logging purposes).
Continuous mode is not used on RS-422/485, because no RTS line is present to
prevent bus contention. However, you can use one meter using a RS-485 board by
configuring the meter for point-to-point continuous mode, and configure it so that it is
enabled at all times. This will result in allowing for transmission to be sent for longer
distances to such devices as large remote displays.
Control of the continuous mode is by RTS level. Either message or character control
can be specified. In the former case, RTS polarity is checked by the meter before a
message is begun, but, once started, the transmission continues to the end of the
specified message. In the latter case, RTS polarity is checked before each character
transmission, so that the meter message can be interrupted after any character.
The specified data and status are transmitted for each new measurement (if so
requested), provided that the selected baud rate and message length are adequate. If
the message transmission takes longer, complete messages are sent as fast as
possible, skipping any readings overlapped by a message transmission.
7. Classes of Operation
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