FPU-16 Modbus Protocol/Data Logger Manual

FPU-16
MODBUS PROTOCOL/DATA LOGGER MANUAL
JULY 1997
PRELIMINARY
Copyright  1997 by Startco Engineering Ltd.
All rights reserved.
Publication: FPU-16-MB-M
Document: S95-F160-000MB
Printed in Canada.
Startco Engineering Ltd.
FPU-16 Modbus Protocol/Data Logger Manual
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Specifications are subject to change without notice. Startco Engineering Ltd. is not liable
for contingent or consequential damages, or for expenses sustained as a result of a
malfunction, incorrect application, or incorrect adjustment.
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Page i
TABLE OF CONTENTS
PAGE
1.
MODBUS PROTOCOL DESCRIPTION .........................................................
1
2.
MODBUS MESSAGE SYNCHRONISATION..................................................
1
3.
ERROR CHECKING .......................................................................................
2
4.
4.1
4.2
4.3
COMMANDS SUPPORTED ...........................................................................
READ REGISTERS AS COILS (CODE 01) ....................................................
READ OUTPUT REGISTERS (CODE 03) ......................................................
WRITE TO REGISTER....................................................................................
4.3.1 MESSAGE FORMAT FOR FUNCTION CODE 06................................
4.3.2 MESSAGE FORMAT FOR FUNCTION CODE 16................................
EXCEPTION RESPONSES.............................................................................
4.4.1 ILLEGAL ADDRESS (CODE 2).............................................................
4.4.2 FPU BUSY (CODE 6) ............................................................................
2
3
3
4
4
5
6
6
6
5.
5.1
FPU SPECIFIC INFORMATION .....................................................................
DATABASES ...................................................................................................
5.1.1 SET POINT MEMORY...........................................................................
5.1.2 DISPLAY MEMORY...............................................................................
5.1.3 RESET MEMORY..................................................................................
5.1.4 TRIP-STATUS-BIT DEFINITIONS ........................................................
5.1.5 ALARM-STATUS-BIT DEFINITIONS ....................................................
5.1.6 MOTOR-STATUS DEFINITIONS ..........................................................
6
6
6
7
8
9
9
9
6.
6.1
6.2
6.3
6.4
FPU-16 DATA LOGGING OPTION .................................................................
CONFIGURATION REGISTERS.....................................................................
REGISTER DEFINITIONS...............................................................................
TRIGGER DEFINITIONS.................................................................................
DATA-LOGGING RECORD FORMAT ............................................................
10
10
10
12
13
7.
FPU-16 STATION-ADDRESS SELECTION ...................................................
13
8.
CONFIGURATION SWITCHES ......................................................................
15
9.
SPECIFICATIONS ...........................................................................................
15
10.
10.1
10.2
INTERFACE CONVERTER.............................................................................
NETWORK INTERCONNECTION ..................................................................
RS-485 TERMINATION...................................................................................
16
16
17
4.4
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FIGURES
FIGURE
PAGE
1
READ COILS ...................................................................................................
3
2
READ OUTPUT REGISTERS ........................................................................
4
3
PRESET SINGLE REGISTER USING CODE 06............................................
5
4
PRESET SINGLE REGISTER USING CODE 16............................................
5
5
RS-232 TO RS-485 CONVERTER..................................................................
18
6
FPU-16 DETAILED APPLICATION USING MODBUS PLC ...........................
19
TABLES
TABLE
PAGE
1
SET POINT MEMORY.....................................................................................
7
2
DISPLAY MEMORY.........................................................................................
8
3
RESET MEMORY............................................................................................
8
4
TRIP-STATUS BITS ........................................................................................
9
5
ALARM-STATUS BITS ....................................................................................
9
6
MOTOR-STATUS BITS ...................................................................................
9
7
CONFIGURATION REGISTERS.....................................................................
10
8
DATA LOGGER RECORD FORMAT..............................................................
13
9
MODE-8 PROGRAM OPTIONS ......................................................................
14
10
BAUD RATE.....................................................................................................
15
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Page 1
FPU-16 MODBUS PROTOCOL
1.
MODBUS PROTOCOL DESCRIPTION
The FPU-16 implements the Modbus RTU protocol as described in the Gould
Modbus Reference Guide, Publication PI-MBUS-300 Rev. B.
The communication system consists of a single master and up to 62 FPU-16
slaves. All devices are connected using two-wire RS-485 network hardware. If the
master does not have an RS-485 port, a RS-232 to RS-485 converter is required.
The converter must have automatic send-data control (SD). SD control does not
require hand-shaking lines since it uses the data line to control the transmit/receive
line on the RS-485 transceivers.
Only the master can initiate a message transaction. Messages can be addressed
to individual slaves or they can be broadcast messages. Broadcast messages are
executed on the FPU-16 slaves but unlike individually addressed messages, the
slaves do not generate a reply message.
2.
MODBUS MESSAGE SYNCHRONISATION
Message synchronisation is accomplished by detection of an idle communication
line. The communication line is considered idle when no communication exists for
an equivalent delay of 3.5 characters.
The first byte received after idle-line detection is interpreted as the address byte of
the next message. Message bytes must be transmitted in a continuous stream
until the complete message has been sent. If a delay of more than 3.5 characters
exists within the message, the message is discarded.
Response messages from the FPU-16 are delayed by at least 3.5 character
delays.
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3.
Page 2
ERROR CHECKING
Modbus RTU uses a 16-bit cyclic redundancy check (CRC). The error check
includes all of the message bytes, starting with the first address byte.
The following procedure generates the CRC for a message:
CONSTANT = A001 (HEX)
CRC_REGISTER = FFFF (HEX)
FOR each data_byte in the message:
GET data_byte
XOR (data_byte, right 8 bits of CRC_REGISTER)
DO 8 times
SHIFT CRC_REGISTER 1 bit to the right
IF bit shifted out was a 1
XOR (CONSTANT, CRC_REGISTER)
END IF
END DO
END FOR
The contents of the CRC_REGISTER is appended to the message with the LSB
first, followed by the MSB.
When a CRC error is detected in the FPU-16, the message is discarded and there
will be no response from the FPU-16.
If the CRC check is correct but the internal data in the message is not correct, the
FPU-16 will respond with one of two exception responses listed in Section 4.4.
4.
COMMANDS SUPPORTED
The FPU-16 Modus Protocol supports three command messages, Read Coils,
Read Output Registers, and Preset Single Register.
In the Modbus Protocol, holding resisters are accessed using function code 03 and
06, and start at 40001 decimal. For example, the first holding register in a 584
would be register 40001 and the output register address generated for the
message would be 0000.
Coils are accessed using function code 1 and are numbered from zero (coil 1 =
zero, coil 2 = one, etc.).
All FPU-16 data can be accessed using the holding register command codes 03
and 06. Alternately, the holding registers can also be read as 16 bits using the
coil-read command code 01.
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4.1
Page 3
READ REGISTERS AS COILS (CODE 01)
Each of the 16 bit registers in the FPU-16 can be read as groups of 16 bits or coils
using this command.
The first byte of the message is the slave address. The second byte is the
function code (01). Bytes three and four specify the starting coil address and the
next two bytes specify the number of coils to read. The last two bytes contain the
CRC code for the message.
The two-byte values of starting coil address and number of coils to read are
transmitted with the high-order byte followed by the low-order byte.
To read a holding register as 16 coils, you specify the starting register number as
the starting coil and request 16 coils.
For example, to read the trip status of holding register 40041 in slave #10 as 16
coils, you specify the starting address as 41 and request 16 coils (coils 41 to 56).
The FPU-16 responds by sending two bytes of information. These two bytes are
interpreted as 2 groups of 8 coils for a total of 16 coils.
READ COILS
HEX BYTE
0A
01
00
28
00
10
BC
B5
DESCRIPTION
Slave Address
Function Code
MSB of First Coil Address
LSB of First Coil Address
MSB of Number of Coils
LSB of Number of Coils
LSB of CRC
MSB of CRC
FIGURE 1
Coils must read in groups of 16 and the starting coil address must be the same as
the register address (except the coils start at 0001 instead of 40001).
4.2
READ OUTPUT REGISTERS (CODE 03)
Read Output Registers allows the user to obtain information from the FPU-16 in
16-bit format.
The first byte of the message is the slave address,. The second byte is the
function code (03). Bytes three and four indicate the starting register. The next
two bytes specify the number of 16-bit registers to read. The last two bytes
contain the CRC code for the message.
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The two-byte values of starting register and number of registers to read are
transmitted with the high-order byte followed by the low-order byte.
The CRC value as calculated in Section 3 is sent with the LSB first followed by the
MSB.
The following message will obtain the value of register 2 (Modbus 40002) from
slave 1. Note that the Modbus registers are numbered from zero (40001 = zero,
40002 = one, etc.).
READ OUTPUT REGISTERS
HEX BYTE
01
03
00
01
00
01
D5
CA
DESCRIPTION
Slave Address
Function Code
MSB Register Address
LSB Register Address
MSB Number of Registers
LSB Number of Registers
LSB CRC
MSB CRC
FIGURE 2
The message length for this message is fixed at 8 bytes.
The addressed slave responds with its address and function code (03), followed by
the information field. The information field contains an 8-bit byte count and the
16-bit data from the slave. The byte count specifies the number of bytes of data in
the information field. The data in the information field consists of 16-bit data
arranged so that the MSB is followed by the LSB.
4.3
WRITE TO REGISTER
Function code 06 or 16 is used to make set-point changes. The FPU-16 does not
allow setting multiple registers so when using function code 16, only one register
should be set.
4.3.1 MESSAGE FORMAT FOR FUNCTION CODE 06
The message to the FPU-16 consists of the FPU-16 address followed by the
function code 06 and two 16-bit values. The first 16-bit value specifies the internal
FPU-16 register to be modified and the second value is the 16-bit data.
Provided no errors occurred, the slave will re-send the original message to the
master. The response message is returned only after the command has been
executed on the FPU-16. This will take approximately 300 ms.
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The following message will set register 4 to 300 in slave #5.
PRESET SINGLE REGISTER USING CODE 06
HEX BYTE
05
06
00
03
01
2C
78
03
DESCRIPTION
Slave Address
Function Code
MSB Register Address
LSB Register Address
MSB of Data
LSB of Data
LSB of CRC
MSB of CRC
FIGURE 3
4.3.2 MESSAGE FORMAT FOR FUNCTION CODE 16
The FPU-16 supports pre-setting a single register using function code 16. Presetting multiple registers is not supported.
Figure 4 shows the message for setting register 4 to 300 in slave #5.
PRESET SINGLE REGISTER USING CODE 16
HEX BYTE
05
10
00
03
00
01
02
01
2C
94
EE
DESCRIPTION
Slave Address
Function Code
MSB Register Address
LSB Register Address
MSB of Quantity (Must be 00)
LSB of Quantity (Must be 01)
Byte Count (Must be 02)
MSB of Data
LSB of Data
LSB CRC
MSB CRC
FIGURE 4
The FPU-16 will reply with the Slave Address, Function Code, Register Address,
and the Quantity followed by the CRC Code for a total of 8 bytes.
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4.4
Page 6
EXCEPTION RESPONSES
The FPU-16 supports two exception responses, Illegal Address and FPU Busy.
The exception message consists of the slave address followed by a retransmission
of the original function code. The function code will have the most-significant bit
set to indicate on error. The 8-bit byte following the function code is the exception
response code. The 16-bit CRC is at the end of the message.
4.4.1 ILLEGAL ADDRESS (CODE 2)
This error indicates that the register number specified in the data field of the
master message is not an allowable register address for the FPU-16.
4.4.2 FPU BUSY (CODE 6)
This error occurs when a valid message was received but the FPU-16 was busy
processing a long duration program command.
The message must be
retransmitted at some later time.
5.
FPU-SPECIFIC INFORMATION
The FPU-16 serial-port data base is updated every 300 ms. Database values can
be read one by one or as a group. Since these values are updated every 300 ms,
the master need not read these values any faster than 300 ms. In the case of set
point-write or reset commands, only one set point or reset command may be
processed every 300 ms.
Unused registers (0x12 to 0x17) must not be included in read/write instructions. If
all information must be retrieved, two instructions are required. One instruction is
used for set-point memory and the other is used for display memory.
5.1
DATA BASE
5.1.1 SET POINT MEMORY
You can read or write to the set-point memory. Individual or groups of set points
can be read; however, set points must be written one at a time and only one set
point may be changed every 300 ms.
Set-point memory is organised in 16 bit words. Data-base values less than 256
will have 0 stored in the high-order byte. Data-base values are transmitted as two
8-bit bytes, with the high byte transmitted first.
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Set-point write instructions must have the data in the 16-bit format. Set-point
values greater than the delete value are forced to the appropriate delete value.
For set points with no delete value, the maximum value of the range is stored.
Set-point values below the minimum are forced to the minimum value.
SET POINT MEMORY
MODBUS
REG.
NO.
NO.
SET POINT (16 BIT)
RANGE
DELETE
INCREMENT
40001
0x00
I²t Trip
1-45
46
1
40002
0x01
I²t Alarm
1-45
46
1
(1)
40003
0x02
Short Time Trip
10-90
91
1
(1)
40004
0x03
Short-Time Alarm
10-90
91
1
(1)
40005
0x04
Instantaneous Trip
10-90
91
1
(1)
40006
0x05
Instantaneous Alarm
10-90
91
1
40007
0x06
Unbalance Trip
5-75
76
1
40008
0x07
Unbalance Alarm
5-75
76
1
40009
0x08
40010
0x09
40011
0x0A
Earth-Leakage Trip
1-100
101
1
40012
0x0B
Earth-Leakage Alarm
1-100
101
1
40013
0X0C
FLA
(.45-.93)*CT-Primary Rating
40014
0x0D
40015
0x0E
Mode 5 Level 1
0-255
1
40016
0x0F
Mode 5 Level 2
0-255
1
40017
0x10
CT-Primary Rating
20-1200
5
40018
0x11
EFCT-Primary Rating
5, 50-2000
50
(1)
Set point is 10 times actual value. A value of 15 corresponds to 1.5 X Phase-CT-Primary
Rating.
TABLE 1
The high-order nibble of Mode 8 level 2 contains the FPU station address. This
value cannot be changed via the serial port.
5.1.2 DISPLAY MEMORY
Display memory is read-only memory organised in 16 bit words. Display values
less than 256 will have 0 stored in the high-order byte. Data-base values are
transmitted as two 8-bit bytes, with the high byte transmitted first.
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DISPLAY MEMORY
MODBUS
NO.
40025
40026
40027
40028
40029
40030
40031
40032
40033
40034
40035
40036
40037
40038
40039
40040
(1)
REG.
NO.
0x18
0x19
0x1A
0x1B
0x1C
0x1D
0x1E
0X1F
0X20
0x21
0x22
0x23
0x24
0x25
0x26
0x27
DESCRIPTION
Phase A Current
Phase B Current
Phase C Current
Unbalance
(1)
Earth Leakage
Percent I²t
Pre-Trip Phase A
Pre-Trip Phase B
Pre-Trip Phase C
Pre-Trip Unbalance
(1)
Pre-Trip Earth Leakage
Pre-Trip I²t
Operation Count
Reset Time
Spare
Station Address of FPU
Trip Status Bits
40041
0x28
Alarm Status Bits
40042
0x29
Motor Status Bits
40043
0x2A
Divide reading by 10 for actual amperes.
Resolution 1/10 A.
TABLE 2
5.1.3 RESET MEMORY
The memory location 0x0078 (40121) is reserved for the reset function and is a
write-only location. The 16-bit data specifies the reset function. A write to register
0x0078 (40121) will perform the function indicated. Only one reset function is
processed every 300 ms.
RESET MEMORY
(2)
DATA
DESCRIPTION
(2)
0000
Null Function
Trip Reset
0001
Latches-Alarm Reset
0002
Not Used
0003
Emergency Thermal Reset
0004
Not Used
0005
FbAd Reset
0006
This function accesses the FPU-16 processor but does not perform any function.
TABLE 3
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5.1.4 TRIP-STATUS-BIT DEFINITIONS
The trip status bits indicate the FPU-16 trip conditions.
TRIP STATUS BITS
BIT NUMBER
0 (LSB)
1
2
3
4
5
6
7
TRIP FUNCTION
1 = I²t Trip
1 = Short-Time Trip
1 = Instantaneous Trip
1 = Unbalance Trip
1 = Earth-fault Trip
Not Used
Not Used
1 = Memory-Fault Trip
TABLE 4
5.1.5 ALARM-STATUS-BIT DEFINITIONS
The alarm-status bits indicate the FPU-16 alarm conditions.
ALARM-STATUS BITS
BIT NUMBER
0 (LSB)
1
2
3
4
5
6
7
ALARM FUNCTION
1 = I²t Alarm
1 = Short-Time Alarm
1 = Instantaneous Alarm
1 = Unbalance Alarm
1 = Earth-fault Alarm
Not Used
Not Used
1 = Memory-Fault Alarm
TABLE 5
5.1.6 FPU-16 STATUS DEFINITIONS
These bits define the FPU status.
MOTOR-STATUS BITS
BIT NUMBER
0 (LSB)
1
FUNCTION
1 = Load Current > 10%
1 = Contact Closed, 0 = Contact Open
TABLE 6
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6.
Page 10
FPU-16 DATA LOGGING OPTION
The FPU-16 data logger captures time-stamped meter data using either a time or
event trigger mechanism. Captured records are stored in non-volatile memory,
which has a data retention of at least 10 years. The real-time clock (RTC)
continues to operate even without control voltage.
Configuration registers are used to configure the data logger. The same command
format as described in section 4 is used for data logger communication. Unlike the
set point and reset memory however, the data logger allows for multiple writes to
the configuration registers.
6.1
CONFIGURATION REGISTERS
Table 7 shows the Modbus and register address location of each configuration
register.
CONFIGURATION REGISTERS
MODBUS
ADDRESS
40129
40130
40131
40132
40133
40134
40135
40136
40137
40138
40139
REGISTER
ADDRESS
0x80
0x81
0x82
0x83
0x84
0x85
0x86
0x87
0x88
0x89
0x8A
DESCRIPTION
MSB: N/A
LSB: Year
MSB: Month
LSB: Date
MSB: Day
LSB: Hour
MSB: Minute
LSB: Second
Sample Interval in Seconds
Trigger Duration Count
Control
Trip Status Trigger Mask
Alarm Status Trigger Mask
FPU-16 Status Trigger Mask
Record Counter (Read Only)
TABLE 7
6.2
REGISTER DEFINITIONS
16-bit registers are used to configure the data logger.
40129: (read/write)
NOT USED (Bits 8:15)
YEAR:
YEAR (Bits 0:7)
00 to 99 BCD
40130: (read/write)
MONTH (Bits 8:15)
MONTH:
DATE:
DATE (Bits 0:7)
01 to 12 BCD
01 to 31 BCD
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40131: (read/write)
DAY (Bits 8:15)
DAY:
HOUR:
HOUR (Bits 0:7)
01 to 07 BCD
00 to 23 BCD
40132: (read/write)
MINUTE (Bits 8:15)
SECOND (Bits 0:7)
MINUTES: 00 to 59 BCD
SECONDS: 00 to 59 BCD
40133: (read/write)
SAMPLE INTERVAL IN SECONDS (Bits 0:15)
SAMPLE INTERVAL: 1 to 65536 Seconds
A sample interval of 0 is not valid.
40134: (read/write)
POST-TRIGGER DURATION (Bits 0:7)
POST-TRIGGER DURATION: 0 to 249 (Valid in Event Mask trigger mode only.).
The duration count specifies the number of additional records captured
after an event-trigger occurs. The time between records is defined by the
sample interval.
If a trigger occurs while the duration counter is active, this record will be
captured but the duration count will not be initialized. The duration count
is initialized only at the occurrence of the first event.
40135: (read/write)
CLOCK ENABLE (Bit 4)
CLEAR COUNTER (Bit 3)
MODE (Bits 0:2)
CONTROL REGISTER:
MODE:
0: Disable data logging.
1: Set trigger to TIME and start recording.
2: Set trigger to EVENT MASK mode and enable trigger.
3 to 7: Not Used.
CLEAR COUNTER:
0: The record counter is not cleared.
1: The record counter is cleared.
This bit is cleared by the data logger when the counter has been cleared.
CLOCK ENABLE:
0: Clock OSC is turned off. (RTC not running)
1: Clock OSC is on.
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40136: (read/write)
16-Bit Trip Status Trigger Mask (Bits 0:15)
TRIP STATUS TRIGGER MASK: Bits that are set in the mask register enables
triggering for the corresponding trip-status bit. For triggering to occur, the
selected trip-status bits must be all zero prior to one of the bits going high.
40137: (read/write)
16-Bit Alarm Status Trigger Mask (Bits 0:15)
ALARM STATUS TRIGGER MASK: Bits that are set in the mask register enables
triggering for the corresponding alarm-status bit. For triggering to occur, the
selected alarm-status bits must be all zero prior to one of the bits going
high.
40138: (read/write)
16-Bit FPU-16 Status Trigger Mask (Bits 0:15)
FPU-16 STATUS TRIGGER MASK: Bits that are set in the mask register enables
triggering for the corresponding FPU-16 status bit. If any of the enabled bits
changes state, triggering occurs.
40139: (read only)
Record Counter
RECORD COUNTER: Counts the number of records captured. This is a read-only
location and is cleared by using the control register.
6.3
TRIGGER DESCRIPTION
With the trigger mode set to TIME, the data logger stores records at fixed time
intervals. The time is defined by SAMPLE INTERVAL. In the TIME mode, any
trip, alarm or FPU-16 status that matches the mask bits will also be recorded.
TRIGGER DURATION does not apply in TIME mode. When the number of
records exceeds 250, new records overwrite old records.
With the trigger mode set to EVENT MASK, the data logger will trigger on a
specific trip, alarm or FPU-16 status condition. The trigger-mask bits define which
trip, alarm or FPU-16 status bits will initiate the trigger. Event mask bit locations
correspond to the trip-status, alarm-status, and FPU-16 status bits defined in the
communications protocol. To enable triggering on a status bit, the corresponding
mask bit is set. All selected bits in the trip or alarm status must be zero to arm the
trigger. When any or all of the bits in the trip or alarm status transition from zero to
one, the data-logger will be triggered. When triggered, the data logger will store
the number of records defined by TRIGGER DURATION with a time interval
defined by the sample unit/interval settings. In the case of the FPU-16 status, not
all bits have to be zero to arm the trigger. Any bit that changes status will cause a
trigger. While in "trigger-duration" mode, event triggering is active, however the
duration counter is initialized on the first trigger condition.
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6.4
Page 13
DATA-LOGGING RECORD FORMAT
Up to 250 records are stored in non-volatile memory. These records are read-only
and are retrieved by specifying the starting address and length for the record.
Each record requires a separate read request. The first record (record 0) is always
the latest record, and record 249 is always the last record. Each record consists of
the following data (Record 0 addresses shown):
DATA LOGGER RECORD FORMAT
MODBUS
ADDRESS
40193
REGISTER
ADDRESS
0xC0
DESCRIPTION
MSB: N/A
LSB: Year
MSB: Month
LSB: Date
MSB: Day
LSB: Hour
MSB: Minute
LSB: Second
Trip Status
Alarm Status
FPU-16 Status
Phase A (A)
Phase B (A)
Phase C (A)
Earth Leakage (x10 A)
2
I t (%)
Operations Count
Pre-Trip Phase A (A)
Pre-Trip Phase B (A)
Pre-Trip Phase C (A)
Pre-Trip Unbalance (%)
Pre-Trip Earth Leakage (x10 A)
2
Pre-trip I t (%)
TABLE 8
The starting address for a record is defined by:
Modbus Address = 40193 + (Record_Number*24) or
Register Address = 0xC0 + (Record_Number*24)
Where Record_Number=0 is the latest record.
NOTE: The record length is a maximum of 24 words or 48 bytes.
7.
FPU-16 STATION-ADDRESS SELECTION
The second level of the Mode-5 program option is used to specify the FPU-16
station address.
Value digits 2 and 3 indicates a decimal address from 0 to 63. Address 0 is the
default value and inhibits serial communication.
Value digit 1 indicates the relay-operating mode.
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Page 14
MODE-5 PROGRAM OPTIONS (2nd Level)
DEFAULT VALUE . . . . . . . . . . 5000
5000
VALUE
DIGIT 1
RELAY OPERATING MODE
0
TRIP-RELAY FAIL SAFE
ALARM RELAY-FAIL SAFE
1
TRIP-RELAY FAIL SAFE
ALARM-RELAY NON FAIL SAFE
2
TRIP-RELAY NON FAIL SAFE
ALARM-RELAY FAIL SAFE
3
TRIP-RELAY NON FAIL SAFE
ALARM-RELAY NON FAIL SAFE
VALUE DIGITS
2 & 3
0
0
6
.
.
.
.
0
1
3
MPU ADDRESS
COMMUNICATIONS INHIBITED
FPU 1
.
.
.
.
FPU 63
TABLE 9
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The FPU-16 supports the Modbus Broadcast Address for write commands only.
Any FPU-16 that is not inhibited (address not zero) will execute broadcast
commands.
8.
CONFIGURATION SWITCHES
Eight DIP switches are located on the back of the communications card. The DIP
switches are accessible through the slot on the back of the FPU-16. When viewed
from the rear, SW1 is the right-most switch. A switch is CLOSED when the
actuator is up (toward the PCB) and OPEN when the actuator is down (away from
the PCB).
Switches 1 to 3 are used to select the communication baud rate.
BAUD RATE
BAUD
SW1
SW2
SW3
SW4 - SW8
9600
OPEN
CLOSED
OPEN (DEFAULT)
NOT USED
4800
CLOSED
CLOSED
OPEN
2400
OPEN
OPEN
CLOSED
1200
CLOSED
OPEN
CLOSED
600
OPEN
CLOSED
CLOSED
300
CLOSED
CLOSED
CLOSED
NOTE: SW6 is used for software-update programming and MUST be in the OPEN position for normal
communications. SW4, SW5, SW7, and SW8 are not used.
TABLE 10
The FPU-16 RS-485 port is fixed at 8 data bits, 1 stop bit, and no parity.
9.
SPECIFICATIONS
Interface ................................................... Isolated RS-485, 2 wire
multi-drop, half duplex.
Protocol .................................................... Modbus RTU
Baud Rate ................................................ 300 to 9600 Baud.
Bit Format................................................. 8 bits, no parity, one stop bit.*
Number of FPU’s Connected................... Maximum of 31 units.}
Line length................................................ 1200 meters total.
Isolation Voltage....................................... 300 Vac continuous
Dielectric................................................... 1500 Vac
*
Terminal 23 (-) is negative with respect to terminal 24 (+) for a binary 1 (MARK or OFF) state.
Terminal 23 (-) is positive with respect to terminal 24 (+) for a binary 0 (SPACE or ON) state.
}
Can be expanded to 62 units with repeater connection.
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10.
Page 16
INTERFACE CONVERTER
A communication master with a RS-232 port requires an RS-232 to RS-485
converter. Two types of converters are available and converter selection depends
upon the hardware/software configuration of the master.
The first type uses hardware control where the RTS line of the RS-232 is used to
control the transmit and receive mode of the RS-485 transceiver. When the RTS
line is high, the transmitter is enabled and when it is low, the transmitter is disabled
and the receiver is enabled. Usually the master software must be specifically
designed for use with this type of control. This type of converter is the most
common type; however, most software packages do not support the hardware
handshaking control.
The second type is the "data only" converter. This converter monitors the data
from the master and sets the transmitter ON or OFF based on activity on the line.
This type of converter requires time to switch from transmit to receive mode. To
avoid RS-485 data collision, a reply or turn-around delay is required at the slave.
This type of converter will work with all software packages that support a
master/slave, half-duplex protocol.
The recommended converter is the Model 485COSR or 485CSP manufactured by
B&B Electronics, and are available from Startco Engineering Ltd. These
converters are "data-only" converters and are configured for operation at 9600
baud. Slower rates require modification to the converter. Consult the factory for
operation below 9600 baud.
10.1
NETWORK INTERCONNECTION
A general diagram is shown in Figure 6 with more detailed wiring diagrams shown
in Figures 4 and 5.
FPU-16 communication ports are interconnected using a two-wire twisted pair
cable. Communication ports are connected in a daisy-chain method. All FPU-16 +
terminals are connected to the white wire, and all FPU-16 - terminals to the black
wire. In the case of the 485CSP, the + terminal is connected too the (B) terminal
and the - terminal to the (A) terminal.
The Model 485COSR and 485CSP are provided with a DB25 connector on the
RS-232 side and a terminal block for the RS-485 side. The RS-232 connector is
the same for both the 485CSP and 485COSR and is a female connector with the
following pins supported.
Pin #
1
2
3
7
Description
Shield ground
Data to converter from computer
Data from converter to computer
Signal ground
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The RS-485 connector is a terminal block with the following designations:
485CSP ADAPTER
DESCRIPTION
FR Shield Ground
TDA RS485 (-)
TDB RS485 (+)
RDA RS485 (-)
RDB RS485 (+)
Signal Ground
Remote Power (+) 12 V
Remote Power (-) GND
485COSR ADAPTER
DESCRIPTION
+ (RS485 Positive)
- (RS485 Negative)
If the converter is at one end of the network, a 150 ohm termination is connected
between (-) and (+) on this connector.
Power for the converter is supplied by an "adapter-type" power supply (Model
485PS) which connects to the + and - terminals of the terminal block.
10.2
RS-485 TERMINATION
Termination resistors are required for line lengths greater than 25 meters.
Termination resistors are normally selected to match the characteristic impedance
of the communication line, and are installed at each end of the network.
When the RS-485 line is idle, all of the RS-485 devices are in a receive state.
Since the line is not driven, the voltage across the twisted-pair cable is zero. This
results in an unknown output state on the master's RS-485 converter which can
cause communication problems with the master software.
To force the RS-485 line to a known state, each FPU-16 has a 100K pull-up
resistor connected from the internal 5-volt supply to the (+) line and a 100K pulldown resistor connected from the (-) terminal to internal circuit ground.
The combination of the pull-up, pull-down, and termination resistances results in a
voltage on the RS-485 line that must be greater than the 200 mV threshold of the
RS-485 receiver to guarantee a valid idle state.
For the RS-485 network used with the FPU-16, the termination consists of a 150
ohm resistor in series with a 0.1 mf capacitor.
This combination satisfies the valid idle-state requirements and provides the 150
ohm termination for the cable.
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Page 18
4-40 SCREW
C/W RETAINER
- +
S
H
RS-232
485C0SR
RS-485
6
1
DB25
FEMALE
TxD 2
GND 7
2 TxD (-)
2
3 RxD (-)
3
SCREW
TERMINAL
2
RS485 (-)
4
SE-TA485
6
RS-232 TO RS-485
CONVERTER
RxD 3
DB25
FEMALE
DB25
MALE
14 TxD (+)
14
16 RxD (+)
16
3
1
1
1 SH
SH
5
7 GND
SH 1
RS485 (+)
NC
25 +
REMOTE
POWER
TERMINAL
ADAPTER
12 -
RS-232 TO RS-485 CONVERTER
FIGURE 5
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RS-232
4
SE-485 COMMUNICATION PACKAGE FOR USE WITH MPU-16A
INCLUDES 485CSP, DC POWER PACK AND (2) SE-TA485
JUMPERS ON 485CSP ARE FACTORY INSTALLED
USE SHIELDED CABLE AND TERMINATION ASSEMBLY SE-TA485
FOR CABLE LENGTHS OVER 50 FEET (15 METERS)
1.
3.
4.
DC
POWER PACK
RD(B)
RD(A)
TD(B)
TD(A)
2.
SE-485
SEE NOTE 2
(485CSP)
RS-485
ADAPTER CABLE PART NUMBER: MPU-16A-BM85-RS232
NOTES:
25 PIN
9 PIN
3 Rx
7 GND
1 SHLD
2 Tx
SHLD 1
Tx 2
Rx 3
DTR 4
GND 5
DSR 6
RTS 7
CTS 8
9
RS-232
RS-232
3
RS-232
2
RS-232
1
MODBUS
BM85
GND
OFF
CONTROL ECH0
RTS SD
ON
+12VDC
RD(B)
TD(B)
RD(A)
TD(A)
FR. GND
SHLD
SE-TA485
NOTE 3
BLK
WHT
SE-TA485
9 PIN MALE TO
25 PIN MALE
ADAPTER CABLE
SEE NOTE 1
23
24
23
24
23
24
23
24
SHIELD
UNIT
1
SHIELD
UNIT
2
UNIT
3
UNIT
4
SHIELD
+
-
SEE NOTE 4
SHIELD
+
-
SEE NOTE 4
+
-
SEE NOTE 4
+
SEE NOTE 4
ICT-2
ICT-2
ICT-2
ICT-2
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FPU-16 Modbus Protocol/Data Logger Manual
Page 19
DETAILED APPLICATION USING MODBUS PLC
FIGURE 6
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