GE 750, Инструкция по эксплуатации

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750/760 Feeder Management Relay GE Power Management
16.3 MODBUS PROTOCOL 16 COMMUNICATIONS
16
16.3.14 READING THE DATA LOGGER
All Data Logger information can be read from Modbus registers found in the address range 2200h to 22ffh. In
order to understand the following description, familiarity with the settings for the Data Logger is required; refer
to Section 8.7: DATA LOGGER on page 8–7. Reading the Data Logger is very similar to reading Trace Memory
and the description for the latter should be used with note of the exceptions described below.
The data channels in the Data Logger are programmable and are determined by the
CHANNEL 1-8 SOURCE
set-
points. These setpoints determine the format of data samples for a given channel.
In Continuous mode the ‘Number of Data Log Triggers Since Last Clear’ is always equal to one.
In Continuous mode the Data Logger only maintains one buffer of 4096 samples for each channel. Since the
buffer is being continuously updated the ‘Data Log Start Index’ will change once the buffer is full and new data
is added (overwriting old data and thus moving the location of the starting index). At slow sampling rates this is
less important but when sampling is performed at a high rate it is very likely that the start index will move
between subsequent reads of the memory map.
In Continuous mode the “Data Log Trigger Index” will always index the last sample added to the buffer. Thus, it
too, will also be quickly and continuously changing if the sampling rate is high.
In Continuous mode the “Data Log Trigger Cause” will be set to zero and the time and date are when the last
sample data was written to the buffer.
16.3.15 ACCESSING DATA VIA THE USER MAP
The 750/760 has a powerful feature, called the User Map, which allows a computer to read up to 120 non-con-
secutive data registers (setpoints or actual values) by using one Modbus packet. It is often necessary for a
master computer to continuously poll various values in each of the connected slave relays. If these values are
scattered throughout the memory map, reading them would require numerous transmissions and would burden
the communication link. The User Map can be programmed to join any memory map address to one in the
block of consecutive User Map locations, so that they can be accessed by reading these consecutive loca-
tions.
The User Map feature consists of User Map Addresses #1 to #120 at locations 0180h to 01F7h in the Memory
Map. These are the setpoints which store the memory map addresses of the values that are to be accessed.
The data registers are read from the
User Map Values #1 to #120 at locations 0100h to 0177h in the Memory
Map. Reading the register at the location of User Map Value #1 returns the value at the address stored in User
Map Address #1 , User Map Value #2 the value at User Map Address #2 , and so on. Storing registers is not
allowed using the User Map.
The following table shows the register addresses to store in the User Map Addresses #1 to #6 so that several
different data registers can be read in one continuous block from User Map Value #1 to #6. Reading the User
Map Values is done via function code 03h or 04h.
The User Memory Map is only intended to be used to READ data in a proficient manner for the
master computer. The communication system should not be configured in a manner that gener-
ates WRITES to these locations continuously, as these settings are stored in the EEPROM that
has a maximum of 100000 program/erase cycles.
NOTE