Page D-3
MPS Motor Protection System Rev. 6-F-022117
Appendix D, MPS A-B DF1 Protocol
D.5 UNPROTECTED READ/WRITE
For PLC-2 and PLC-3 processors not supporting Typed
Read/Write messages, Unprotected Read/Write
commands can be used. For these messages, the data
address is the Octal value of the MPS Register in
Appendix E. The size is the number of registers. The
maximum number of registers that can be transferred in a
single message is 100.
Unprotected Read/Write commands are used by the
SE-Comm-MPS communication program.
D.6 TYPED LOGICAL READ/WRITE
The Typed Logical Read (CMD = 0F, FNC = A2) and
Typed Logical Write (CMD = 0F, FNC = AA) messages are
supported by the full line of SLC 500 processors and Prosoft
MVIxx-DFCM communication interfaces.
Both float (F) and integer (N) types are supported.
Unlike the typed commands in Section D.3 and D.4 a file
offset is not required for integer values. Use the A-B file
address as listed in the MPS manual Appendix E and
precede the address with F for float values and N for integer
values.
The maximum number of integers and floats that can be
read is 100 and 50 respectively.
Reset commands to the MPS are issued by writing one of
the COMMAND CODES listed in Table D.2 to Register 6
(N3:6).
D.7 DATA RECORDS
Only one event record can be read at a time. Data is for
the record indicated by the Record Selector. To select a
record, write the record number to Record Selector and then
read the values in the record. Record-Head points to the
next available record. The last event record captured is at
Record Head minus one.
Both Record-Selector and Record-Head values are in the
range of 0 to 63. Values outside this range will select
record 0.
D.8 CUSTOM DATA ACCESS
Data access can be customized with the User-Defined
Registers and the User Data Register.
Enter the required data-register numbers in the User-
Defined Registers. The format of user data is a function of
the corresponding register.
To access the data, read the corresponding User-Data
Register.
D.9 NETWORK TIMEOUT
The MPS can be configured to trip or alarm on a network
timeout using the Setup | Hardware | Network Comms
menu. The Net Trip Action and Net Alarm Action set points
set the actions to be taken when a timeout occurs. To
prevent a timeout, a valid message, addressed to the slave,
must be received at time intervals less than five seconds.
NOTE: Set protocol to None before selecting Network Error
actions; then, select protocol.
D.10 SPECIFICATIONS
Interface ........................................ Isolated RS-485, 2-wire,
multi-drop, half duplex
Protocol ........................................ Modbus RTU
Baud Rate ..................................... 1,200 to 19,200 bit/s
(3)
Bit Format .................................... 8 bits, no parity, one stop
bit
(1)
Number of CTU's Connected ...... Maximum of 32 units
Bus length ..................................... 1,200 m (4,000’) total
(2)
(1)
Terminal “-” is negative with respect to terminal “+” for
a binary 1 (MARK or OFF) state.
Terminal “-” is positive with respect to terminal “+” for
a binary 0 (SPACE or ON) state.
(2)
For line lengths exceeding 10 m (30’), 150-Ω terminations
are required at the cable ends.
(3)
Error rate is 1 byte/120 kB at 19,200 bit/s. For high
reliability, use 9600 bit/s.
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