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B.5.4: Log Retrieval
Log Retrieval is accomplished in 3 basic steps:
1.
Engage the log.
2.
Retrieve each of the records.
3.
Disengage the log.
B.5.4.1: Auto-Increment
In EIG's traditional Modbus retrieval system, you write the index of the block of data to retrieve,
then read that data from a buffer (window). To improve the speed of retrieval, the index can be
automatically incremented each time the buffer is read.
®
In the Shark
200 meter, when the last register in the data window is read, the record index is
incremented by the Records per Window.
B.5.4.2: Modbus Function Code 0x23
QUERY
Field Name
Slave Address
Function
Starting Address Hi
Starting Address Lo
# Points Hi
# Points Lo
Repeat Count
Function Code 0x23 is a user defined Modbus function code, which has a format similar to
Function Code 0x03, except for the inclusion of a "repeat count." The repeat count (RC) is
used to indicate that the same N registers should be read RC number of times. (See the
Number of Repeats bullet on the previous page.)
NOTES:
The response for Function Code 0x23 is the same as for Function Code 0x03, with the data
blocks in sequence.
IMPORTANT: Before using function code 0x23, always check to see if the current
connection supports it. Some relay devices do not support user defined function codes; if that
is the case, the message will stall. Other devices don't support 8 repeat counts.
E
Electro Industries/Gauge Tech
By itself this feature would not provide any advantage, as the same data will be
returned RC times. However, when used with auto-incrementing, this function
condenses up to 8 requests into 1 request, which decreases communication time,
as fewer transactions are being made.
®
In the Shark
200 meter repeat counts are limited to 8 times for Modbus RTU,
and 4 times for Modbus ASCII.
Example (Hex)
01
23
C3
51
00
7D
04
Doc# E149701
B-11
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