Multi-point Digital Controller
MA900/MA901
Communication
Instruction Manual
RKC INSTRUMENT INC.
®
IMR01H02-E3
!"Modbus is a registered trademark of Schneider Electric.
!"Company names and product names used in this manual are the trademarks or registered trademarks of
the respective companies.
All Rights Reserved, Copyright 2001, RKC INSTRUMENT INC.
Thank you for purchasing this RKC instrument. In order to achieve maximum performance and ensure
proper operation of your new instrument, carefully read all the instructions in this manual. Please
place this manual in a convenient location for easy reference.
SYMBOLS
WARNING
CAUTION
!
: This mark indicates precautions that must be taken if there is danger of electric
shock, fire, etc., which could result in loss of life or injury.
: This mark indicates that if these precautions and operating procedures are not
taken, damage to the instrument may result.
: This mark indicates that all precautions should be taken for safe usage.
: This mark indicates important information on installation, handling and operating
procedures.
: This mark indicates supplemental information on installation, handling and
operating procedures.
: This mark indicates where additional information may be located.
WARNING
!
An external protection device must be installed if failure of this instrument
!"
could result in damage to the instrument, equipment or injury to personnel.
All wiring must be completed before power is turned on to prevent electric
!"
shock, fire or damage to instrument and equipment.
This instrument must be used in accordance with the specifications to prevent
!"
fire or damage to instrument and equipment.
This instrument is not intended for use in locations subject to flammable or
!"
explosive gases.
Do not touch high-voltage connections such as power supply terminals, etc.
!"
to avoid electric shock.
RKC is not responsible if this instrument is repaired, modified or
!"
disassembled by other than factory-approved personnel. Malfunction can
occur and warranty is void under these conditions.
IMR01H02-E3
i-1
CAUTION
This is a Class A instrument. In a domestic environment, this instrument may cause radio
!
interference, in which case the user may be required to take adequate measures.
This instrument is protected from electric shock by reinforced insulation. Provide
!
reinforced insulation between the wire for the input signal and the wires for instrument
power supply, source of power and loads.
Be sure to provide an appropriate surge control circuit respectively for the following:
!
- If input/output or signal lines within the building are longer than 30 meters.
- If input/output or signal lines leave the building, regardless the length.
This instrument is designed for installation in an enclosed instrumentation panel. All high-
!
voltage connections such as power supply terminals must be enclosed in the
instrumentation panel to avoid electric shock by operating personnel.
All precautions described in this manual should be taken to avoid damage to the
!
instrument or equipment.
All wiring must be in accordance with local codes and regulations.
!
All wiring must be completed before power is turned on to prevent electric shock,
!
instrument failure, or incorrect action.
The power must be turned off before repairing work for input break and output failure
including replacement of sensor, contactor or SSR, and all wiring must be completed
before power is turned on again.
To prevent instrument damage or failure, protect the power line and the input/output lines
!
from high currents with a protection device such as fuse, circuit breaker, etc.
Prevent metal fragments or lead wire scraps from falling inside instrument case to avoid
!
electric shock, fire or malfunction.
Tighten each terminal screw to the specified torque found in the manual to avoid electric
!
shock, fire or malfunction.
For proper operation of this instrument, provide adequate ventilation for heat dispensation.
!
Do not connect wires to unused terminals as this will interfere with proper operation of the
!
instrument.
Turn off the power supply before cleaning the instrument.
!
Do not use a volatile solvent such as paint thinner to clean the instrument. Deformation or
!
discoloration will occur. Use a soft, dry cloth to remove stains from the instrument.
To avoid damage to instrument display, do not rub with an abrasive material or push front
!
panel with a hard object.
Do not connect modular connectors to telephone line.
!
NOTICE
!
This manual assumes that the reader has a fundamental knowledge of the principles of electricity,
process control, computer technology and communications.
!
The figures, diagrams and numeric values used in this manual are only for purpose of illustration.
!
RKC is not responsible for any damage or injury that is caused as a result of using this instrument,
instrument failure or indirect damage.
!
Periodic maintenance is required for safe and proper operation of this instrument. Some
components have a limited service life, or characteristics that change over time.
!
Every effort has been made to ensure accuracy of all information contained herein. RKC makes no
warranty expressed or implied, with respect to the accuracy of the information. The information in
this manual is subject to change without prior notice.
!
No portion of this document may be reprinted, modified, copied, transmitted, digitized, stored,
processed or retrieved through any mechanical, electronic, optical or other means without prior
written approval from RKC.
i-2
IMR01H02-E3
CONTENTS
Page
1. OUTLINE ...............................................................................1
2. SPECIFICATIONS................................................................. 2
3. WIRING .................................................................................5
4. SETTING ...............................................................................8
4.1 Transfer to Setup Setting Mode ......................................................................8
4.2 Setting the Communication Parameters..........................................................9
4.3 Communication Requirements ......................................................................13
5. RKC COMMUNICATION PROTOCOL ............................... 15
5.1 Polling............................................................................................................15
5.1.1 Polling procedures ............................................................................................16
5.1.2 Polling procedure example (Multi-point mode)..................................................21
5.1.3 Polling procedure example (Single mode) ........................................................24
5.2 Selecting........................................................................................................25
5.2.1 Selecting procedures........................................................................................25
5.2.2 Selecting procedure example (Multi-point mode)..............................................30
5.2.3 Selecting procedure example (Single mode) ....................................................33
5.3 Communication Identifier List ........................................................................34
6. MODBUS COMMUNICATION PROTOCOL ....................... 44
6.1 Message Format ...........................................................................................44
6.2 Function Code ...............................................................................................45
6.3 Communication Mode ...................................................................................45
6.4 Slave Responses ..........................................................................................46
6.5 Calculating CRC-16.......................................................................................47
IMR01H02-E3
i-3
Page
6.6 Message Format............................................................................................49
6.6.1 Read holding registers [03H] ............................................................................49
6.6.2 Preset single register [06H] ..............................................................................50
6.6.3 Diagnostics (loopback test) [08H] .....................................................................51
6.6.4 Preset multiple registers [10H]..........................................................................52
6.7 Data Configuration ........................................................................................52
6.7.1 Data range........................................................................................................53
6.7.2 Data processing precautions ............................................................................54
6.8 Communication Data List ..............................................................................55
6.9 Data Map.......................................................................................................62
6.9.1 Reference to data map .....................................................................................62
6.9.2 Data map list.....................................................................................................63
7. INPUT RANGE TABLES..................................................... 75
8. TROUBLESHOOTING ........................................................ 79
9. ASCII 7- BIT CODE TABLE ................................................82
i-4
IMR01H02-E3
1. OUTLINE
Multi-point Digital Controller MA900/MA901 interfaces with the host computer via Modbus or RKC
communication protocols.
In RKC communication, there are the data format (multi-point mode) in which the MA900/MA901 is
used as a multi-point controller (for the MA900: 4 channels and for the MA901: 8 channels) and
that (single mode) used as multidrop-connected with a single controller.
In addition, the three types of communication interfaces are available: RS-422A, RS-485 and
RS-232C.
For reference purposes, the Modbus protocol identifies the host computer as master, the
MA900/MA901 as slave.
RS-422A or RS-485
!"
Host computer
RS-422A or RS-485
RS-232C
!"
MA900
or
MA901
Host computer
MA900
or
MA901
MA900
or
MA901
RS-232C
MA900
or
MA901
MA900
or
MA901
･････････
MA900
or
MA901
IMR01H02-E3
1
2. SPECIFICATIONS
RKC communication
!"
!"
!"!"
Interface: Based on RS-422A, EIA standard
Based on RS-485, EIA standard
Based on RS-232C, EIA standard
(Specify when ordering)
Connection method: 4-wire system, half-duplex multi-drop connection (RS-422A)
2-wire system, half-duplex multi-drop connection (RS-485)
3-wire system, point-to-point connection (RS-232C)
Synchronous method: Start-stop synchronous type
Communication speed: 2400 bps, 4800 bps, 9600 bps, 19200 bps
Data bit configuration: Start bit: 1
Data bit: 7 or 8
Parity bit: Without, Odd or Even
Stop bit: 1 or 2
Protocol: ANSI X3.28 subcategory 2.5, A4
Polling/selecting type
Error control: Vertical parity (With parity bit selected)
Horizontal parity (BCC check)
Communication code: ASCII 7-bit code
Termination resistor: Externally connected (RS-485)
Xon/Xoff control: None
Maximum connections: Multi-point mode (MA900/MA901)
RS-422A, RS-485: 32 instruments maximum including a host computer
RS-232C: 1 instrument
Single mode (MA900) *
RS-422A, RS-485: 26 instruments maximum including a host computer
RS-232C: 1 instrument
Single mode (MA901) *
RS-422A, RS-485: 13 instruments maximum including a host computer
RS-232C: 1 instrument
* As the address setting range is from 00 to 99, addresses corresponding to four
MA900s or eight MA901s are used in the single mode.
Therefore, the connectable number of sets is limited.
2
IMR01H02-E3
Signal logic: RS-422A, RS-485
Signal voltage Logic
V (A) - V (B) ≥ 2 V 0 (SPACE)
V (A) - V (B) ≤ -2 V 1 (MARK)
Voltage between V (A) and V (B) is the voltage of (A) terminal
for the (B) terminal.
RS-232C
Signal voltage Logic
+3 V or more 0 (SPACE)
-3 V or less 1 (MARK)
2. SPECIFICATIONS
Modbus
!"
!"
!"!"
Interface: Based on RS-422A, EIA standard
Based on RS-485, EIA standard
Based on RS-232C, EIA standard
(Specify when ordering)
Connection method: 4-wire system, half-duplex multi-drop connection (RS-422A)
2-wire system, half-duplex multi-drop connection (RS-485)
3-wire system, point-to-point connection (RS-232C)
Synchronous method: Start/stop synchronous type
Communication speed: 2400 bps, 4800 bps, 9600 bps, 19200 bps
Data bit configuration: Data bit: 8 (Byte data corresponding to binary data or bit.)
Parity bit: Without, Odd or Even
Stop bit: 1 or 2 (However, with the parity bit selected: 1 bit fixed)
Protocol: Modbus
Signal transmission mode: Remote Terminal Unit (RTU) mode
Function code: 03H (Read holding registers)
06H (Preset single register)
08H (Diagnostics: loopback test)
10H (Preset multiple registers)
IMR01H02-E3
3
2. SPECIFICATIONS
Error check method: CRC-16
Error code: 1: Function code error
2: When any address other than 0000H to 02EEH and 1388H to 14A0H
are specified
3: When the specified number of data items in the query message
exceeds the maximum number of data items available
4: Self-diagnostic error response
Termination resistor: Externally connected (RS-485)
Maximum connections: RS-422A, RS-485: 32 instruments maximum including a master
RS-232C: 1 instrument
Signal logic: RS-422A, RS-485
Signal voltage Logic
V (A) - V (B) ≥ 2 V 0 (SPACE)
V (A) - V (B) ≤ -2 V 1 (MARK)
Voltage between V (A) and V (B) is the voltage of (A) terminal
for the (B) terminal.
RS-232C
Signal voltage Logic
+3 V or more 0 (SPACE)
-3 V or less 1 (MARK)
4
IMR01H02-E3
3. WIRING
WARNING
!
To prevent electric shock or instrument failure, do not turn on the power until all
the wiring is completed.
Connection to the RS-422A port of the host computer (master)
!"
Communication terminal number and signal details
#"
Terminal No. Signal name Symbol
44 Signal ground SG
45 Send data T (A)
46 Send data T (B)
47 Receive data R (A)
48 Receive data R (B)
Wiring method
#"
MA900/MA901
(Slave)
T (A)
T (B)
R (A)
R (B)
Communication terminals
$
$
$
MA900/MA901
(Slave)
T (A)
T (B)
SG
SG
Paired wire
RS-422A
44
45
46
47
48
Host computer (Master)
SG
T (A)
T (B)
R (A)
R (B)
Shielded twisted
pair wire
44
45
46
Communication terminals
IMR01H02-E3
R (A)
47
48
R (B)
Maximum connections: Multi-point mode: 31 instruments (MA900/MA901)
Single mode: 25 instruments (MA900)
12 instruments (MA901)
The cable is provided by the customer.
5
3. WIRING
Connection to the RS-485 port of the host computer (master)
!"
!"
!"!"
Communication terminal number and signal details
#"
#"
#"#"
Terminal No. Signal name Symbol
44 Signal ground SG
45 Send data/Receive data T/R (A)
46 Send data/Receive data T/R (B)
Wiring method
#"
#"
#"#"
MA900/MA901
(Slave)
SG
RS-485
44
Paired wire
Host computer (Master)
SG
T/R (A)
45
T/R (B)
Communication terminals
46
$
$
$
MA900/MA901
(Slave)
44
SG
T/R (A)
T/R (B)
Communication terminals
45
46
The cable is provided by the customer.
T/R (A)
T/R (B)
*R
Shielded twisted
pair wire
*R
Maximum connections: Multi-point mode: 31 instruments (MA900/MA901)
Single mode: 25 instruments (MA900)
Single mode: 12 instruments (MA901)
*R: Termination resistors
(Example: 120 Ω 1/2 W )
6
IMR01H02-E3
Connection to the RS-232C port of the host computer (master)
!"
!"
!"!"
Communication terminal number and signal details
#"
#"
#"#"
Terminal No. Signal name Symbol
44 Signal ground SG (GND)
45 Send data SD (TXD)
46 Receive data RD (RXD)
Wiring method
#"
#"
#"#"
3. WIRING
MA900/MA901
(Slave)
SG (GND)
SD (TXD)
RD (RXD)
Communication terminals
Number of connection: 1 instrument
44
45
46
RS-232C
Shielded wire
Host computer (Master)
SG (GND)
SD (TXD)
RD (RXD)
*
RS (RTS)
CS (CTS)
Short RS and CS within connector.
*
The cable is provided by the customer.
Connection example (For the MA900/MA901 multi-point mode)
!"
!"
!"!"
Connection with up to 31 MA900/MA901 (slaves) and one host computer (master)
Host computer (Master)
Device address
(Slave address)
IMR01H02-E3
1 2
MA900/MA901
RS-422A
or
RS-485
Junction terminals
3 4 29 30 31
MA900/MA901
(Slave)
(Slave)
7
4. SETTING
To establish communication parameters between host computer (master) and MA900/MA901 (slave),
it is necessary to set the device address (slave address), communication speed, data bit configuration
and interval time on each MA900/MA901 (slave) in the setup setting mode.
Power ON
Input Type/Input Range Display
(Display for approx. 4 seconds)
Display changes automatically
PV/SV Monitor Mode
Press and hold the
SET key and press
the <R/S key at the
same time
If the key is not pressed for
more than one minute, the
display will automatically
return to the PV/SV display
mode.
Setup Setting Mode
(Setting the communication
parameters)
Power is turned on again
(Registration of set value)
4.1 Transfer to Setup Setting Mode
To go the setup setting mode, you must be in PV/SV monitor mode. The first parameter to be
displayed will be the autotuning, ATU. Press the SET key several times to change to the device
address “Add.”
PV
SV
SET
R/S
PV/SV monitor mode
PV
SV
SET
R/S
AREA
CH
CH
MA900
Setup setting mode
Autotuning (AT) setting
PV
SV
SET
R/S
AREA
CH
CH
MA900
Device address setting
(Slave address)
AREA
CH
CH
MA900
When let setup setting mode finish, press and hold the SET key and press the <R/S key at
the same time. The display changes to the PV/SV monitor mode.
MA900 is used in the above figures for explanation, but the same setting procedures also
apply to MA901.
8
IMR01H02-E3
4. SETTING
4.2 Setting the Communication Parameters
To select parameters in setup setting mode, press the SET key. The parameters are displayed and
sequenced in the order of device address (slave address), Add, communication speed, bPS, data bit
configuration, bIT and interval time set value, InT.
Setting procedure
!"
Setting procedure vary depending on the communication parameter.
Device address
•
Operate UP, DOWN and <R/S key, and input numerals.
, interval time
Add
InT
Communication speed
•
, data bit configuration
bPS
bIT
Operate UP or DOWN key, and choose one among the displayed set value.
For MA900: Proportioning cycle time setting (heat control) or
Cool-side proportioning cycle time setting (heat/cool control)
For MA901: Proportioning cycle time setting
Press the SET key.
PVCH
SVAREA
Device address [Add]
(Slave address)
PVCH
SVAREA
Interval time [InT]
Press the SET key.
Press the SET key.
Press the SET key.
PVCH
SVAREA
Communication speed
PVCH
SVAREA
Data bit configuration
[bPS]
Press the SET key.
[bIT]
Scan interval time
Registration of set value
!"
After completing all communication parameter settings, turn on the power again, and register the set
value which changed.
After the power is turned on again, communication is mode using the set value changed.
Not by turning the power on again, the set value can also be registered by changing to RUN
from STOP.
IMR01H02-E3
9
4. SETTING
Description of each parameters
!"
!"
!"!"
Symbol Name Setting range Description Factory
Device address
(Slave address)
(Add)
0 to 99
(See P.16, 17)
Set it not to duplication in multidrop connection.
If the slave address is set to 0 in
Modbus, two-way communication
cannot be performed.
Set the same communication
speed for both the MA900/MA901
(slave) and the host computer
(master).
Set the same data bit configuration
for both the MA900/MA901
(slave) and the host computer
(bPS)
(bIT)
Communication
speed
Data bit
configuration
240: 2400 bps
480: 4800 bps
960: 9600 bps
1920: 19200 bps
data bit
See
configuration
table
(master).
Interval time * 0 to 250 ms The MA900’s or MA901’s
interval time must match the
(InT)
specifications of the host
computer.
set value
0
960
8n1
10
Data bit configuration table
Set value Data bit Parity bit Stop bit
(8n1) 8 Without 1
(8n2) 8 Without 2
(8E1) 8 Even 1
1
(8E2)
8Even2
Setting range of
Modbus
(8o1) 8 Odd 1
1
(8o2)
1
(7n1)
1
(7n2)
1
(7E1)
1
(7E2)
1
(7o1)
1
(7o2)
1
When the Modbus communication protocol selected, this setting becomes invalid.
8 Odd 2
7 Without 1
7 Without 2
7Even1
7Even2
7 Odd 1
7 Odd 2
Setting range of
RKC communication
* The interval time for the MA900/MA901 should be set to provide a time for host computer to finish
sending all data including stop bit and to switch the line to receive data. If the interval time between
the two is too short, the MA900/MA901 may send data before the host computer is ready to receive
it. In this case, communication transmission can not be conducted correctly. For a successful
communication sequence to occur, the MA900’s or MA901’s interval time must match the
specifications of the host computer.
10
No setting can be changed when “1: Lock” is selected by the lock level 1.
For the lock level 1, see the Instruction Manual (IMR01H01-E
####
).
IMR01H02-E3
Setting procedure example
!"
!"
!"!"
MA900 is used in the below figures for explanation, but the same setting procedures also
apply to MA901.
Go to the setup setting mode so that device address (slave address), Add, is displayed.
1.
Present set value is displayed, and the least significant digit light brightly.
4. SETTING
PV
SV
SET
R/S
AREA
CH
CH
MA900
Device address setting
(Slave address)
2. Set the device address. Press the UP key to enter 5 at the least significant digit.
Example: Setting the device address (slave address) to 15.
PV
SV
AREA
CH
CH
MA900
3. Press the <R/S key to brightly light the tens digit.
CH
AREA
CH
MA900
IMR01H02-E3
SET
SET
R/S
PV
SV
R/S
11
4. SETTING
4. Press the UP key to enter 1 at the tens digit.
PV
SV
SET
R/S
AREA
CH
CH
MA900
5. Press the SET key to set the value thus set. The display changes to the next communication
parameter. It the SET key is not pressed within 1 minute, the present display returns to the
PV/SV monitor mode and the value set here returns to that before the setting is changed.
PV
SV
SET
R/S
AREA
CH
CH
MA900
Communication speed setting
6. After completing all communication parameter settings, turn on the power again, and register the
set value which changed. After the power is turned on again, communication is made using the
set value changed.
Besides power on again, register of set value with RUN/ STOP transfer. In this case, have to
change to STOP before setting communication parameter. Change to RUN after completing
the communication parameter settings, the instrument performs the same operation as that at
the time of power on again.
In addition, it the communication parameter is changed at RUN, communication is made
using the set value changed if returned to RUN once set to STOP.
For the RUN/STOP transfer, see the Instruction Manual (IMR01H01-E
$$$$
).
12
IMR01H02-E3
4. SETTING
4.3 Communication Requirements
Processing times during data send/receive
!"
!"
!"!"
The MA900/MA901 requires the following processing times during data send/receive.
Whether the host computer is using either the polling or selecting procedure for communication, the
following processing times are required for MA900/MA901 to send data:
-Response wait time after MA900/MA901 sends BCC in polling procedure
-Response wait time after MA900/MA901 sends ACK or NAK in selecting procedure
RKC communication (Polling procedure)
Procedure details Time (ms)
MIN TYP MAX
Response send time after MA900/MA901 receives ENQ 1 2 4
Response send time after MA900/MA901 receives ACK 1
Response send time after MA900/MA901 receives NAK 1
Response send time after MA900/MA901 sends BCC
−
−
−−
4
4
1
RKC communication (Selecting procedure)
Procedure details Time (ms)
MIN TYP MAX
Response send time after MA900/MA901 receives BCC 1 2 3
Response wait time after MA900/MA901 sends ACK
Response wait time after MA900/MA901 sends NAK
Modbus
Procedure details Time
Read holding registers [03H]
Response transmission time after the slave receives the query
message
Preset single register [06H]
Response transmission time after the slave receives the query
message
Diagnostics (loopback test) [08H]
Response transmission time after the slave receives the query
message
Preset multiple registers [10H]
Response transmission time after the slave receives the query
message
−−
−−
20 ms max.
3 ms max.
3 ms max.
20 ms max.
1
1
IMR01H02-E3
Response send time is time at having set interval time in 0 ms.
13
4. SETTING
RS-485 (2-wire system) send/receive timing
!"
!"
!"!"
The sending and receiving of RS-485 communication is conducted through two wires; consequently,
the transmission and reception of data requires precise timing. Typical polling and selecting
procedures between the host computer and MA900/MA901 are described below:
Polling procedure
%"
%"
%"%"
Send data
(Possible/Impossible)
Host computer
Sending status
Send data
Controller
a
: Response send time after MA900/MA901 receives [ENQ] + Interval time
b
: Response send time after MA900/MA901 sends BCC
c
: Response send time after MA900/MA901 receives [ACK] + Interval time or
(Possible/Impossible)
Sending status
Possible
Impossible
Possible
Impossible
E
O
- - - - -
T
E
N
Q
bca
S
- - - - -
T
X
B
C
C
A
C
K
Response send time after MA900/MA901 receives [NAK] + Interval time
N
or
A
K
Selecting procedure
%"
%"
%"%"
Send data
(Possible/Impossible)
Host computer
Sending status
Send data
Controller
a:
Response send time after MA900/MA901 receives BCC + Interval time
b:
Response wait time after MA900/MA901 sends ACK or Response wait time after MA900/MA901
(Possible/Impossible)
Sending status
Possible
Impossible
Possible
Impossible
S
- - - - -
T
X
B
C
C
ba
N
A
or
A
C
K
K
sends NAK
To switch the host computer from transmission to reception, send data must be on line. To
check if data is on line, do not use the host computer’s transmission buffer but confirm it by
the shift register.
Whether the host computer is using either the polling or selecting procedure for
communication, the following processing times are required for MA900/MA901 to send data:
-Response wait time after MA900/MA901 sends BCC in polling procedure
-Response wait time after MA900/MA901 sends ACK or NAK in selecting procedure
RS-422A/RS-485 Fail-safe
!"
!"
!"!"
A transmission error may occur with the transmission line disconnected, shorted or set to the highimpedance state. In order to prevent the above error, it is recommended that the fail-safe function be
provided on the receiver side of the host computer. The fail-safe function can prevent a framing error
from its occurrence by making the receiver output stable to the MARK (1) when the transmission line
is in the high-impedance state.
14
IMR01H02-E3
5. RKC COMMUNICATION PROTOCOL
p
[
]
[
]
[
]
p
The MA900/MA901 (hereafter, called controller) uses the polling/selecting method to establish a data
link. The basic procedure is followed ANSI X3.28 subcategory 2.5, A4 basic mode data transmission
control procedure (Fast selecting is the selecting method used in this controller).
!"The polling/selecting procedures are a centralized control method where the host computer
controls the entire process. The host computer initiates all communication so the controller
responds according to queries and commands from the host.
!"The code use in communication is 7-bit ASCII code including transmission control characters.
The transmission control characters are EOT (04H), ENQ (05H), ACK (06H), NAK (15H),
STX (02H) and ETX (03H). The figures in the parenthesis indicate the corresponding
hexadecimal number.
In RKC communication, both multi-point and single modes are available. If the single mode
is required, contact our sales office or agent.
5.1 Polling
Polling is the action where the host computer requests one of the connected controllers to transmit
data. An example of the polling procedure is shown below:
Host com
E
[Address] [ ] [ ID ]
O
T
(1)
(2)
Memory area
number
uter send
Host
Controller send
E
N
Q
No res
E
O
(4)
T
S
ID
T
X
onse
(5)
Data
E
T
X
BCC
(3)
computer
send
(8)
No
response
Controller
send
Time
out
(9)
Indefinite
(6)
A
C
N
K
A
K
(7)
Host
computer
send
E
O
T
(10)
E
O
T
ID: Identifier
IMR01H02-E3
15
5. RKC COMMUNICATION PROTOCOL
5.1.1 Polling procedures
(1) Data link initialization
Host computer sends EOT to the controllers to initiate data link before polling sequence.
(2) Data sent from host computer - Polling sequence
The host computer sends the polling sequence in the following two types of formats:
• Format in which no memory area number is specified, and
• Format in which the memory area number is specified.
When no memory area number is specified
#"
To be sent in this format for any identifier not corresponding to the memory area.
3.1.
IdentifierAddress
When the memory area number is specified
#"
4.
Example:
1
1M0
To be sent in this format for any identifier corresponding to the memory area.
2.1.
Memory
area
number
4.3.
IdentifierAddress
Example:
1
1. Address (2 digits)
• Multi-point mode
ENQENQ
S11KK0
ENQENQ
16
The device address specifies the controller to be polled and each controller must have its own
unique device address.
For details, see 4.2 Setting the Communication Parameters (P. 9).
IMR01H02-E3
5. RKC COMMUNICATION PROTOCOL
• Single mode
This data represents the device address and channel number of the controller to be polled. When
polling any identifier without the corresponding channel number, the channel number is ignored.
Each address is calculated as follows.
Calculation method of address:
Address = Device address of controller + Controller channel number - 1
Example: When 3 controllers (MA900: 4 channels) are multidrop-connected
Device address
of controller
Controller
channel number
Addresses used in
polling sequence
Controller 1 Device address 00 + CH1 - 1 = Address 00
Device address 00 + CH2 - 1 = Address 01
Device address 00 + CH3 - 1 = Address 02
Device address 00 + CH4 - 1 = Address 03
Controller 2 Device address 04 + CH1 - 1 = Address 04
Device address 04 + CH2 - 1 = Address 05
Device address 04 + CH3 - 1 = Address 06
Device address 04 + CH4 - 1 = Address 07
Controller 3 Device address 08 + CH1 - 1 = Address 08
Device address 08 + CH2 - 1 = Address 09
Device address 08 + CH3 - 1 = Address 10
Device address 08 + CH4 - 1 = Address 11
Set the device address number of the succeeding controller to four or more than four plus the same
number of the previous controller. Otherwise (for example, if set to 00, 01 and 02 between Controllers
1, 2 and 3), the address used for polling is duplicated and as a result no normal communication can be
made.
For example, if Address 10 is
selected CH3 corresponding to
Controller 3 is urged to send
data.
In case of the MA901:
Set the device address number of the succeeding controller to eight or more than eight plus the
same number of the previous controller.
Controller 1: Device address 00, Controller 2: Device address 08, ..........
2. Memory area number (2 digits)
This is the identifier to specify the memory area number. It is expressed by affixing “K” to the
head of each memory area number (from 1 to 8). In addition, if the memory area number is
assigned with “K0,” this represents that control area is specified.
The memory area now used for control is called “Control area.”
If the memory area number is not specified when polling the identifier corresponding to
the memory area, this represents that the control area is specified.
If any identifier not corresponding to the memory area is assigned with a memory area
number, this memory area number is ignored.
IMR01H02-E3
17
5. RKC COMMUNICATION PROTOCOL
3. Identifier (2 digits)
The identifier specifies the type of data that is requested from the controller.
For details, see 5.3 Communication Identifier List (P. 34).
4. ENQ
The ENQ is the transmission control character that indicates the end of the polling sequence.
The ENQ must be attached to the end of the identifier.
The host computer then must wait for a response from the controller.
(3) Data sent from the controller
If the polling sequence is received correctly, the controller sends data in the following format:
3.2. 5.4.1.
STX
Identifier Data BCC
ETX
1. STX
STX is the transmission control character which indicates the start of the text transmission
(identifier and data).
2. Identifier (2 digits)
The identifier indicates the type of data (measured value, status and set value) sent to the host
computer.
For details, see 5.3 Communication Identifier List (P. 34).
3. Data
Data which is indicated by an identifier of this controller, consisting of channel numbers, data,
etc. It is expressed in decimal ASCII code including a minus sign (-) and a decimal point.
Channel number: 2 digit ASCII code, not zero-suppressed.
(Channel number: MA900: from 01 to 04, MA901: from 01 to 08)
Channels without channel numbers may exist depending on the type identifier.
In addition, in case of single mode, do not use the channel number.
Data: ASCII code. The number of digits varies depending on the type of identifier.
Multi-point mode: Zero-suppressed with spaces (20H).
Single mode: Not zero-suppressed.
18
Data structure of identifier with channel number (Only for multi-point mode)
A data is divided from that of the next channel with a comma.
number
Space
DataChannel
Comma
Channel
number
Space
Data
For the identifier without the corresponding channel number, the same data is sent to the
host computer regardless of the channel number.
,,
Comma
IMR01H02-E3
5. RKC COMMUNICATION PROTOCOL
4. ETX
ETX is a transmission control character used to indicate the end of text transmission.
5. BCC
BCC (Block Check Character) detects error using horizontal parity and is calculated by
horizontal parity (even number).
Calculation method of BCC: Exclusive OR all data and characters from STX through ETX, not
including STX.
Example:
BCCETX0001M005STX
03H30H30H35H30H30H30H31H4DH
Hexadecimal numbers
BCC = 4DH ⊕ 31H ⊕ 30H ⊕ 30H ⊕ 30H ⊕ 35H ⊕ 30H ⊕ 30H ⊕ 03H = 7AH
Value of BCC becomes 7AH.
(4) EOT sent from the controller (Ending data transmission from the controller)
In the following cases, the controller sends EOT to terminate the data link:
• When the specified identifier is invalid
• When there is an error in the data type
• When data is not sent from the host computer even if the data link is initialized
• When all the data has been sent
(5) No response from the controller
The controller will not respond if the polling address is not received correctly. It may be necessary for
the host computer to take corrective action such as a time-out.
(6) ACK (Acknowledgment)
An acknowledgment ACK is sent by the host computer when data received is correct. When the
controller receives ACK from the host computer, the controller will send any remaining data of the
next identifier without additional action from the host computer.
For the identifier, see #### Communication identifier list (P. 35).
When host computer determines to terminate the data link, EOT is sent from the host computer.
(7) NAK (Negative acknowledge)
If the host computer does not receive correct data from the controller, it sends a negative
acknowledgment NAK to the controller. The controller will re-send the same data when NAK is
received. This cycle will go on continuously until either recovery is achieved or the data link is
corrected at the host computer.
IMR01H02-E3
19
5. RKC COMMUNICATION PROTOCOL
(8) No response from host computer
When the host computer does not respond within approximately three seconds after the controller
sends data, the controller sends EOT to terminate the data link. (Time out: 3 seconds)
(9) Indefinite response from host computer
The controller sends EOT to terminate the data link when the host computer response is indefinite.
(10) EOT (Data link termination)
The host computer sends EOT message when it is necessary to suspend communication with the
controller or to terminate the data link due lack of response from the controller.
20
IMR01H02-E3
5. RKC COMMUNICATION PROTOCOL
5.1.2 Polling procedure example (Multi-point mode)
Four channels specification of MA900 is used in the procedure example for explanation, but
the same setting procedures also apply to MA901. However, the 8-channel specification
applies to the MA901. Therefore, refer to procedure examples by replacing the 4-channel
specification for the MA900 with the 8-channel specification for the MA901.
(1) When no memory area number is specified
Normal transmission
!"
Host computer send
E
0 0 M 1
O
T
Device
address
Identifier
E
N
Q
S
M 1 0 1 1 00 . 0 , 0 2 2 00 . 0 ,
T
X
Identifier
Channel
number
Space
Controller send
Data
Comma
Channel
number
Data
Space
Continue to *1
*1
0 3 3 00 . 0 , 0 4 4 00 . 0
Error transmission
!"
Host computer send
E
0 0 M 1
O
T
Device
address
Identifier
*1
......
4 4 00 . 0
Controller send
E
B
T
C
X
C
Channel
number
Error dataE
Data
Space
Host computer send
N
A
K
E
B
T
C
X
C
Controller send
Comma
Channel
number
Controller re-sendController send
S
M 1 0 1 0 01 . 0 ,
T
X
N
Q
S
M 1 0 1 1 00 . 0 , 0 2 2 00 . 00,
T
X
Identifier
A
C
K
Data
Space
Controller send
S
M 2 0 1 ......
T
X
......
......
Host computer sendHost computer send
E
B
T
C
X
C
Continue to *1
Host computer send
E
O
T
E
B
T
C
X
C
E
O
T
IMR01H02-E3
21
Loading...