865.1
7
RWF40...
Interface RS-485
The RS-485 interface is used for integrating RWF40… controllers into data networks
via MOD bus protocol.
Application examples:
-
-
-
Process visualization
Plant control
Reporting
Master-slave principle
Communication between a PC (master) and a device (slave) via MOD bus is based on
the master-slave principle in the form of data query / instruction – reply.
A master computer controls the exchange of data and can address up to 99 controllers
via device addresses (slaves).
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Communication sequence
Both the start and end of a data block are characterized by transmission pauses. The
maximum period of time that may elapse between 2 successive characters is 3 times
the period of time required for the transmission of one character.
The character transmission time (period of time required for the transmission of 1 char-
acter) is dependent on the Baud rate and the type of data format.
Using a data format of 8 data bits, no parity bit and 1 stop bit, the character transmis-
sion time is calculated as follows:
Character transmission time [ms] = 1000 * 9 bits / Baud rate
Process
Data query by the master
Transmission time = n characters * 1000 * x bits / Baud rate
Identification of end of data query
3 characters * 1000 * x bits / Baud rate
Handling of data query by the slave (? 250 ms)
Reply by the slave
Transmission time = n characters * 1000 * x bits / Baud rate
Identification of end of reply
3 characters * 1000 * x bits / Baud rate
Example
Identification of the data query or end of the reply with a data format of 10 / 9 bits.
Waiting time = 3 characters * 1000 * x bits / Baud rate
Baud rate
9.600
19.200
Data format [bits]
Waiting time [ms]
2.813
9
9
1.406
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Data query sequence
The time sequence of a data query looks as follows:
Time sequence
Master
Slave
Data query
Data query
Reply
t0
t1
t0
t2
7865z12e/1102
t0
t1
t2
Identification of end = 3 characters
(time is dependent on the Baud rate)
This time is dependent on internal handling.
The maximum handling time is 250 ms
This is the time required by the device to switch from the transmitting mode back
to the receiving mode.
This time must be observed by the master before it makes a new data query. It
must always be maintained, even if the new data query is sent to some other
device.
t2 O 20 ms
Communication during the slave’s internal handling time
The master is not allowed to make any data queries during the slave’s internal handling
time.
Data queries made during that period of time will be ignored by the slave.
Communication during the slave’s response time
The master is not allowed to make any data queries during the slave’s response time.
Data queries made during that period of time cause all data currently on the bus to
become obsolete.
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Structure of the data blocks
All data blocks use the same structure:
Data structure
Slave address
Function code
Data field
Checksum CRC16
1 byte
1 byte
x byte
2 bytes
Every data block contains 4 fields:
Slave address
Function code
Data field
Device address of a certain slave
Function selection (reading or writing words)
Contains the following information:
-
-
-
Word address
Number of words
Word value
Checksum
Identification of transmission errors
Fault handling
3 different error codes are used:
Error codes
1
2
8
Invalid function
Invalid parameter address
Write access to parameter rejected
Reply in the event
of fault
Slave address
Function
XX OR 80 h
1 byte
Error code
Checksum CRC16
1 byte
1 byte
2 bytes
The function code is OR linked with 0 x 80, that is, the MSB (most significant bit) will be
set to 1.
Example
Data query:
01
Reply:
01
02
00
70
00
04
CRC16
82
01
CRC16
Special cases
In the following cases, the slave does not reply:
-
-
-
The checksum (CRC16) is wrong
The instruction given by the master is incomplete or overdefined
The number of words or bits to be read is zero
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Checksum (CRC16)
The checksum (CRC16) is used to detect transmission errors.
If the evaluation reveals an error, the relevant device will not respond.
Calculation
CRC = 0xFFF
CRC = CRC XOR ByteOfMessage
For (1 to 8)
CRC = SHR (CRC)
if (flag to the right = 1)
then
else
CRC = CRC XOR
0xA001
while (not all ByteOfMessage edited)
The low byte of the checksum will be transmitted first.
ꢀ
Example
Data query:
Reading 2 words from address 6 (CRC16 = 0x24A0)
0B
03
00
06
00
02
A0
24
CRC16
Reply:
(CRC16 = 0x6105)
0B 03
04
00
00
42
C8
61
05
Word 1
Word 2
CRC16
The following functions for the device will be available:
Function number
0x03 / 0x04
0x06
Function
Reading n words (n ? 12)
Writing 1 word
0x10
Writing n words (n ? 2)
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Reading n words
This function is used to read n words from a certain address.
Slave address Function 0x03 Address of the Number of
Data query
Checksum
CRC16
or 0x04
first word
words
(max. 12)
2 bytes
1 byte
1 byte
2 bytes
2 bytes
Reply
Slave address Function 0x03
or 0x04
Number of
bytes read
1 byte
Word value(s)
Checksum
CRC16
2 bytes
1 byte
1 byte
x byte(s)
Example
Reading the 2 setpoints of the controller
Word address = 0x0008 (setpoint SP1)
Data query:
0B
Reply:
0B
03
00
08
00
04
CRC16
03
08
0000
42C8
0000
4316
CRC16
Setpoint 1 (100)
Setpoint 2 (150)
Writing 1 word
With the “Wordwriting” function, the data blocks for instruction and reply are identical.
Instruction
Slave address Function 0x06 Word address
1 byte 1 byte 2 bytes
Slave address Function 0x06 Word address
1 byte 1 byte 2 bytes
Word value
2 bytes
Checksum
CRC16
2 bytes
Reply
Word value
2 bytes
Checksum
CRC16
2 bytes
Example
Write limit value limit comparator 1 (AL1) (= 275)
Word address = 0x000C
Instruction: (write the first part of the value)
0B
Reply (like instruction):
0B 06
06
00
00
0C
0C
80
80
43
43
00
00
89
89
CRC16
CRC16
CRC16
CRC16
Instruction: (write the second part of the value)
0B
Reply (like instruction):
0B 06
06
00
00
0D
0D
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Writing n words
Slave
address
Function
0x10
Address Number of Number of
Word
value(s)
Check-
sum
CRC16
2 bytes
Instruction
of first
word
words
bytes
(max. 2)
1 byte
1 byte
1 byte
2 bytes
2 bytes
x byte(s)
Reply
Slave address Function 0x10
1 byte 1 byte
Address of
first word
2 bytes
Number of
words
2 bytes
Checksum
CRC16
2 bytes
Example
Write switch-on threshold (Hys1 = -10)
Word address = 0x0018
Instruction:
0B
10
00
18
00
02
04
00
00
00
C1
20
CRC16
CRC16
Reply:
0B
10
00
18
02
Data type “char“
Data type “float“
The high byte must be transmitted first.
Example: Configuration code C111: “9030“
MOD bus: 0B10 0024 00 02 04 0903
The following explanations apply under the condition that the master works with the
IEEE-754 format. Before transmitting a value, the bytes must be exchanged in a way
that the order corresponds to the presentation for the MOD bus (see illustration below).
M-23 bit normalized mantissa
E-exponent (complement to base 2)
S-Sign-bit; 1 = negative, 0 = positive
MOD-Bus
MMMMMMMM
EMMMMMMM
MMMMMMMM
SEEEEEEE
Master
(IEEE 754)
EMMMMMMM
SEEEEEEE
MMMMMMMM MMMMMMMM
7865z13e/1102
Example:
Transmission of decimal value “550“:
MOD bus:
0x80, 0x00, 0x44, 0x09
Following is a description of all process values (variables) with their addresses, data
type and type of access.
Where:
R / O
R / W
float
Read only access
Read and write access
Float value (4 bytes / 2 words)
Integer (2 bytes / 1 word)
word
The process values are subdivided into logic areas.
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Address tables
Process data
Address
Data
Access
Parameter
Value range
Default
value
type
float
float
float
float
0x0000
0x0002
0x0004
0x0006
R / O
R / O
R / O
R / W
Actual value E1
Actual value E2
Actual value E3
Current setpoint
0x0008
0x000A
float
float
R / W SP1
R / W SP2 (=dSP) Second setpoint
First setpoint
SPL...SPH
SPL...SPH
0
0
Parameter level
Address
Data
Access
Parameter
Value range
Default
type
float
float
float
float
float
float
float
float
float
float
float
float
value
0
10
80
350
1
15
-5
3
5
0
1.0
0
0x000C
0x000E
0x0010
0x0012
0x0014
0x0016
0x0018
0x001A
0x001C
0x001E
0x0020
0x0022
R / W AL
R / W Pb1
R / W dt
R / W rt
R / W db
R / W tt
R / W Hys1
R / W Hys2
R / W Hys3
Limit value limit comparator
Proportional band
Derivative action time
Integral action time
Dead band (neutral zone)
Actuator running time
Switch-on threshold
Switch-off threshold, bottom
Switch-off threshold, top
Reaction threshold
Heating curve slope
Parallel displacement
room temperature
-1999...9999
0.1...9999
0...9999
0...9999
0.0...100.0
10...3000
0...-199.9
0...Hys3
0.0...999.9
0.0...999.9
0.0...4.0
R / W
R / W
R / W
q
H
P
-90...90
Configuration level
Address
Data
type
char [4]
char [4]
char [4]
char [4]
Access
Parameter
Value range
Default
value
9030
0010
0110
0x0024
0x0026
0x0028
0x002A
R / W C111
R / W C112
R / W C113
R / W C000
0000
0x002C
0x002E
0x0030
0x0032
0x0034
0x0036
0x0038
0x003A
0x003C
0x003E
0x0040
0x0042
0x0044
0x0046
0x0048
float
float
float
float
float
float
float
float
float
float
float
float
float
float
float
R / W SCL
R / W SCH
R / W SCL2
R / W SCH2
R / W SPL
R / W SPH
R / W OFF1
R / W OFF2
R / W OFF3
R / W HYST
R / W df1
Normalization start value: Input 1
Normalization end value: Input 1
Normalization start value: Input 2
Normalization end value: Input 2
Start value setpoint limitation
End value setpoint limitation
Offset input 1
-1999...9999
-1999...9999
-1999...9999
-1999...9999
-1999...9999
-1999...9999
-1999...9999
-1999...9999
-1999...9999
0...9999
0.0...100.0
0...1440
0...7200 *
-1999...9999
-1999...9999
0
100
0
100
0
100
0
0
Offset input 2
Offset input 3
0
1
Hysteresis of limit comparator
Filter time constant input 1
Filter time constant input 3
Bus detection timer
Start value actual value limit
End value actual value limit
1.0
1278
30
-1999
9999
R / W dF3
R / W dtt
R / O oLLo
R / O oLHi
* Timer = 0 means switched off
This parameter can only be changed via the management system
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Device data
Address
Data
type
Access
Parameter
Value range
Default
value
0x0300
0x0300
0x0306
word [13]
R / O Device data
char SWVersion [11+1]
char VDNNr [13+1]
Software version
VdN number
Remote operation
Address
Data
type
Access
Parameter
Value range
Default
value
0x0400
float
R / O TEMP
Actual value E3 (unfiltered)
0x0500
0x0501
word
word
R / W REM
R / W ROFF
Activation remote operation
Controller OFF in REMOTE
SETPOINT
0...2 *
0...1 **
0
0
0x0502
0x0504
float
float
R / W RHYS1
R / W RHYS2
Switch-on threshold REMOTE
Switch-off threshold bottom
REMOTE
0...-1999
0...RHYS3
HYS1
HYS2
0x0506
0x0508
float
float
R / W RHYS3
R / W SPR
Switch-off threshold top REMOTE
Setpoint REMOTE
0...9999
SPL...SPH
HYS3
SP1
0x050A
0x050B
0x050C
0x050D
0x050E
0x050F
word
word
word
word
word
float
R / W RK1
R / W RK2
R / W RK3
R / W RK6
R / W RSTEP
R / W RY
Burner control remote operation
Relay K2 remote operation
Relay K3 remote operation
Relay LK remote operation
Step control remote operation
Positioning output remote
operation
0...1
0...1
0...1
0
0
0
0
0
0
0...1
-100...100
0...100
*
0 = local
** 1 = controller OFF
1 = remote setpoint
2 = fully remote
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Device state
Address
Data type
Access
Parameter
0x0200
word
R / O
Outputs and states
B15 B14 B13 B12 B11 B10 B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
B8
B9
Hysteresis limitation
B0
B1
B2
B3
Output 1 off
Output 3 off
Output 2 off
Output 4 off
(for remote operation)
Management system off
(for remote operation)
Self-optimization active
Second setpoint active
Measured value range crossing input 1
Measured value range crossing input 2
Measured value range crossing input 3
Reserved
B10
B11
B12
B13
B14
B15
0x0201
word
R / O
Binary signal and hardware identification
B15 B14 B13 B12 B11 B10 B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
B15
B14
B13
Reserved
Interface present
Analog output present
B0
B1
B2
B3
B4
B5
B6
B7
Operating mode 2-stage active
Manual operation active
Binary input 1 closed
Binary input 2 closed
Thermostat function active
First controller output active
Second controller output active
Limit comparator active
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Description of operating modes
General
Parameter «RemoteStatus» is used to switch between the operating modes «LOCAL»,
«REMOTE SETPOINT» and «FULLY REMOTE». The change is always accomplished
via the MOD bus.
In the event the master fails or communication is lost, the RWF40... will switch to oper-
ating mode «LOCAL». The time for detecting a failure is set via the interface.
RAM parameter for re-
mote operation
Remote
Default after
«Power-up»
parameter
REM
Operating mode «LOCAL», «REMOTE SETPOINT» or
«FULLY REMOTE»
= 0
SPR
Setpoint remote
= SP1
RHYS1
RHYS2
RHYS3
ROFF
Switch-on threshold remote
= Hys1
= Hys2
= Hys3
Lower switch-off threshold remote
Upper switch-off treshold remote
)
Controller ON (0) / OFF (1) in operating modes
«REMOTE SETPOINT» and «FULLY REMOTE»
Number of control cycles (opening / closing) (FULLY
REMOTE)
= 0 ¹
)
RSTEP
= 0 ²
)
RK1
RK2
RK3
RK6
Release of burner (FULLY REMOTE)
Controlling element opens (FULLY REMOTE)
Controlling element closes (FULLY REMOTE)
Value of «K6» in operating modes «SETPOINT
REMOTE» and «FULLY REMOTE»
Degree of modulation for the analog output (FULLY
REMOTE) in %
= 0 ³
)
= 0 ³
)
= 0 ³
= 0
RY
= 0
)
¹
²
³
Controller active
)
)
No travel command (K2 + K3 = deenergized)
When the operating mode changes (e.g. LOCAL J FULLY REMOTE), the relay
information and the degree of modulation will be predefined, depending on the
operating state of the plant.
Dtt
Bus detection timer (value will also be maintained after a power failure)
The remote parameters are stored in RAM and will no longer be available after a power
failure.
After «Power-up», the default values will be used.
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Operating mode
«LOCAL»
The previous functions of the RWF40... are maintained (apart from memory usage).
The RWF40... can be parameterized and uploaded via the MOD bus, whereby the out-
puts cannot be changed. After «Power-up», the RWF40... will normally assume oper-
ating mode «LOCAL».
Operating mode
The RWF40... monitors cyclic bus communication via the «Dtt» parameter (bus detec-
tion timer). Operating mode «REMOTE SETPOINT» is active as long as the bus calls
within the predefined period of time. If the time limit is crossed, the RWF40... will switch
to operating mode «LOCAL» and continues to operate using the parameters of local
operation.
«REMOTE SETPOINT»
Like in operating mode «LOCAL», the control functions of the RWF40... are maintained.
With regard to setpoint and switching thresholds, only «RSP» and «RHYS1...RHYS3»
are active. The setpoints (SP1 and SP2), the external setpoint, the weather-
compensated setpoint, the analog / binary setpoint shift and the associated changeover
functions are not available.
After the controller’s «Power-up», setpoint «SP1» and switching thresholds
«Hys1...Hys3» will be copied to RAM as remote parameters in a one-time operation.
These remote parameters can then only be changed via the management system.
The control algorithm can be deactivated by the management system via parameter
«ROFF=1». In that case, the RWF40... will switch the burner off and causes the con-
trolling element to travel to the fully closed position. The controller terminates manual
operation (analog safety shutdown).
Self-optimization is not possible in this operating mode.
The management system controls contact «RK6» (relay «K6»).
Operating mode
The RWF40... monitors cyclic bus communication via the «Dtt» parameter (bus detec-
tion timer). Operating mode «FULLY REMOTE» is active as long as the bus calls within
the predefined period of time. If the time limit is crossed, the RWF40... will switch to
operating mode «LOCAL» and continues to operate using the parameters of local op-
eration.
«FULLY REMOTE»
The management system switches the burner (RK1, relay «K1»), controls the actuator
(RK2 and RK3, relays «K2 / K3»), or defines the degree of modulation in the case of an
analog output, and controls contact «RK6» (relay «K6»).
Using parameter «ROFF=1», control of the burner and controlling element can be
switched off by the management system. In that case, the RWF40... deactivates the
burner and causes the controlling element to travel to the fully closed position.
Manual operation and self-optimization are not possible in this operating mode.
2-stage burner:
If, with a 2-stage burner, relay positions «RK2» and «RK3» are identical, the settings
are «K2 = deenergized» and «K3 = energized» (closing).
The analog output is set as follows, depending on the relay positions «RK2» and
«RK3»:
K2 = energized, K3 = deenergized J analog output = 10 V or 20 mA
K2 = deenergized, K3 = energized J analog output = 0 V or 0 / 4 mA
Setting the «RY» by the management system has no impact.
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Mudulating burner
Modulating controller:
The management system predefines the value (degree of modulation) for the analog
output via «RY».
Setting the «RK2» and «RK3» by the management system has no impact.
Both relays «K2» and «K3», are deenergized.
Floating step controller:
The management system controls the actuator («RK2» and «RK3», relays «K2» /
«K3»).
Setting the «RY» by the management system has no impact. In that case, the analog
output delivers 0 V or 0 / 4 mA.
The RWF40... always checks to ensure that «RK2» and «RK3» (opening / closing) are
not activated simultaneously. In such a case, the response is «K2 = K3 = deener-
gized».
If both relay contacts change their position during the controller’s sequence time, the
output is «K2 = K3 = deenergized». This time contact interval («K2 = K3 = off» for one
scanning time) is also permitted in 2-stage operation.
Control strategy for
floating output with
modulating burner
operation
The remote relay commands «RK2» and «RK3» (relays «K2» / «K3») control the
opening and closing travel of the controlling element. Using parameter «RSTEP», the
management system predefines the required number of control cycles.
Output «K2» (opening) is controlled by a travel command and a positive number.
Output «K3» (closing) is controlled by a travel command and a negative number.
The number gives the number of RWF40... scanning cycles (210 ms) with which the
output is controlled.
The travel command with number 0 deenergizes immediately «K2» and «K3».
If a new travel command is given before the control time has elapsed, the RWF40...
ascertains the direction of rotation requested by the command. If the direction of rota-
tion does not change, the control time will immediately be replaced by the new value. If
the direction of rotation must be reversed, the controlled output will be dactivated and,
for the next scanning cycle, the appropriate control time is used (time contact interval).
If, simultaneously with the control strategy for the floating output, outputs «K2» and
«K3» (via «RK2» and «RK3») are directly set by the management system, the relay
information from the control strategy and output information «K2» and «K3» have a
logic «OR» connection. «RK2» and «RK3» (opening / closing) must never be energized
simultaneously. In such a case, the response is «K2 = K3 = denergized».
Supervision of actual
value by setpoint-
dependent switching
thresholds
In operating mode «FULLY REMOTE», the management system ensures burner con-
trol. The RWF40... monitors the actual value to make certain the switching hystereses
will be observed.
If the actual value crosses the upper switch-off threshold, the management system will
be locked (status flag, «Management system locked» can be read via the interface).
The management system is released again when the actual value returns to a level
below the switch-on threshold.
If supervision of the actual value is not desired, the switching hystereses in the
RWF40... must be set to the respective maximum value.
In operating mode «REMOTE SETPOINT», the control algorithm ensures this kind of
supervision.
ꢀ2002 Siemens Building Technologies
Subject to change!
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