9.17
Date Code 20120126
Instruction Manual
SEL-2032 Communications Processor
Protocols
Modbus RTU Protocol
Your Modbus master will require many read messages to access the data in
this setup—at least one message per relay. On top of this, the floating-point
processing required to convert each data item can cause response times to
increase to 2.5 seconds or longer. However, if you move all data to a single
User Region on an SEL-2032 port, your Modbus master may be able to read
all required data with a single Modbus read, allowing data update rates as fast
as one second. See
Example 6: Modbus Job Done on page 3.26
for an example
of accessing centralized data in the SEL-2032.
Force Single Coil (Function Code 05h)
The SEL-2032 uses this function code for a variety of data control purposes.
Specifically, you can use it to clear archive records, hold copies of data
records, release copies of data records, and operate breaker and remote bit
elements.
The master request must have the following format:
1 byte.
Slave Address
1 byte.
Function Code (05h)
2 bytes.
Coil Reference
2 bytes.
Operation Code
2 bytes.
CRC–16 for Message
A successful SEL-2032 response is an echo of the request message.
There are six special purpose coil references:
0000h.
Clear archive record using function code 04h addressing
0003h.
Copy a region using function code 04h addressing
0004h.
Release a region copy using function code 04h addressing
0010h.
Clear archive record using function code 03h addressing
0013h.
Copy a region using function code 03h addressing
0014h.
Release a region copy using function code 03h addressing
Coil references 0000h and 0010h are for clearing archive records. The
operation code must be the starting address of the record to clear. Once you
clear an archive record, subsequent reads from that region will return data
from the next record stored in that region.
NOTE
: Frequent archive record
clearing may exceed EEPROM
capabilities. See the discussion in
Archive Data Regions on page 6.21
.
Coil references 0003h and 0013h cause a copy of the specified region to be
made. Subsequent reads from this region will read from your copy. This
allows you to read data regions that are larger than 125 registers without the
data changing between accesses. Specify the region to copy by giving its
starting address as the operation address. Use coil references 0004h and 0014h
to release the region copy once you are done with it. If there is insufficient
memory to make the requested copy, the SEL-2032 will respond with a BUSY
exception code.
For coil references 0000h, 0003h, and 0004h, the operation code must
correspond to a modified map address (map function code 04h uses). For
operation codes 0010h, 0013h, and 0014h, this starting address must
correspond to a true database address.
Coil references 10AOh–10BFh correspond to the port breaker and remote bit
elements. See
for a list of coil references for these elements.
NOTE:
Response times will increase
when using function code 04h to
access a large amount of Modbus
specific map data. Whenever
possible, concentrate required data
items close to the beginning of the
USER region for efficient data reads
and quicker response times.
Summary of Contents for SEL-2032
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