Section 13. Control of the frequency converter by means of connection RS
13. Control of the frequency converter by means of connection RS
Frequency converter MFC710 is equipped with RS232 communication link and/or RS485 (depending on variant). It
enables to control work of device with help of a computer or an external controller. The basic characteristics and
possibilities of the RS link of the frequency converter:
•
operation with speed 9600, 19200, 38400 or 57600 bits per second,
•
a format of a character: 8 data bits, lack of parity control, 2 stop bits,
•
transfer protocol: MODBUS mode RTU,
•
check of transfer validity with use of CRC sum,
•
unit number (converter) set up with help of parameter (typically 12),
•
support of MODBUS commands: command 3 - “read the register” - allows to read individual registers from the
converter or block of up to 127 registers. command 6 - “register write” - write to individual register in the
converter,
•
possibility of reading of an operating mode, control start/stop, reading and writing of referencing-units,
•
possibility of reading and writing of all parameters of the converter just as by means of a control panel,
•
possibility of reading all 512 PCH and writing 64 of them, which are intended for writing through RS connection.
All operations are based on two basic commands of MODBUS RTU protocol - 3 and 6 which are described in
publications concerning МODBUS.
13.1. Parameters which concern communication through RS
Table 13.1 - Parameters which refer to communication
Parameter
Description
2.2
Referencing-unit A - it is possible to set up a source "RS"
2.3
Referencing-unit B - it is possible to set up a source "RS"
2.4
Start A - it is possible to set up a source "RS"
2.5
Start B - it is possible to set up a source "RS"
4.7
RS permission – it is possible to enable permanent permission to control from RS, disable permanent permission or, for
example, set enabling/disabling RS permission from a digital input. The permission concerns referencing frequency
through RS, RS PID referencing-unit, and a START / STOP/BLOCKING signal from RS (see table 13.2 - registers 2000,
2001 and 2002).
4.8
RS speed - possible options is 9600, 19200, 38400, 57600 bits per second.
4.9
Number of device (converter) in MODBUS protocol (possibility of connecting several converters through one
communication channel RS 485).
CAUTION:
If control RS blocked (par. 4.7), and parameters 2.2, 2.3, 2.4 or 2.5 define control as "RS" in this case the
frequency converter remains in STOP mode or the referencing-unit of frequency will assume value 0.
13.2. Map of registers accessible through RS link
All registers are 16-bit numbers. Addresses which are omitted in the table are not supported.
Table 13.2 - Registers
The address
of the
registers
(decimal)
Description (meaning)
Mode
PCH REGISTERS
1000 ... 1383
PCH from number 0 up to number 383 (see. Appendix A)
Read only
1384 ... 1447
PCH from number 384 up to number 447 - intended for writing through RS (see. Appendix A)
Read / write
1448 ... 1511
PCH from number 448 up to number 511 (see. Appendix A)
Read only
REGISTERS OF OPERATING MODES
2000
The register RS CONTROL. The data is valuable only when the parameter 4.7 (RS permission)
allows control of the device with RS. Bits meaning:
bits 0 - not used
bits 1 - the sequence 0 → 1 → 0 erases the message on failure
bits 2,3 - not used
bits 4 - 1 = force referencing PID from RS (the register 2002)
bits 5 - 1 = force referencing frequency from RS (the register 2001)
bits 6 - 1 = force START/STOP Control from RS
bits 7,8,9,10,11 - not used
bits 12 - 1 = BLOCKING of OPERATION shut down according to Parameter
bits 13 - 1 = BLOCKING of OPERATION shut down RAMP
bits 14 - 1 = BLOCKING of OPERATION shut down RUN OUT
bits 15 - 1 = START 0 = STOP
Bits 4,5,6 allow to force control of the drive through communication channel RS even if referencing-
units or source of START / STOP signal is set up on value which differs from RS. If, for example, the
referencing-units A is set up on value "RS" , to set frequency with RS, there is no necessity to set up
bit 5. Forcing of control with RS by means of bits 4,5,6 results in switching off a source of the control
established with parameters.
Bits 12,13,14 block operation of the drive irrespective of the established type of control (also when,
for example, there is control through RS and bits 15 = 1).
Read / write
The last
value written
down in this
register cab
be read.
Frequency converter MFC710 type. TWERD Power Electronics
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