AL2-MBU Advanced Manual

Transcription

1 AL2-MBU Advanced Manual REVISION December 2008

2 REVISION LIST January 2008 Preliminary version June 2008 First official release December 2008 New feature: Force Multiple Coils Specific Registers for AlphaXL timeout THE INFORMATION CONTAINED IN THIS DOCUMENT ARE SUBJECT TO CHANGE WITHOUT NOTICE. PRODUCT NAMES, CORPORATE NAMES, OR TITLES USED WITHIN THIS DOCUMENT MAY BE TRADEMARKS OR REGISTERED TRADEMARKS OF OTHER COMPANIES, AND ARE MENTIONED ONLY IN AN EXPLANATORY MANNER TO THE READERS BENEFIT, AND WITHOUT INTENTION TO INFRINGE. WHILE EVERY EFFORT HAS BEEN MADE TO MAKE SURE THE INFORMATION IN THIS DOCUMENT IS CORRECT, CONTRIVE CAN NOT BE LIABLE FOR ANY DAMAGES WHATSOEVER FOR LOSS RELATING TO THIS DOCUMENT. MODBUS IS A REGISTERED TRADEMARK OF SCHNEIDER ELECTRIC. COPYRIGHT 2008 CONTRIVE SRL ITALY.ALL RIGHT RESERVED. AL2-MBU Advanced Manual - 1

3 1. INTRODUCTION TO MODBUS MODBUS REGISTER MAP AL2 Outputs AL2 External Outputs AL2 Link Outputs AL2 Communication Bit devices AL2 System Bit AL2 Inputs AL2 External Inputs AL2 Link Inputs AL2 Analog Inputs AL2 Communication W ord devices MODBUS SERIAL TRANSMISSION MODE Baud Rate Parit y AlphaXL communication timeout MODBUS ADDRESSES MODBUS FUNCTIONS Read Coil Status Example Read Input Status Example Read Holding Register Example Read Input Registers Example Force Single Coil Example Force Multple Coils Example Preset Single Register Example Device Identification Categories of objects Identification request AL2-MBU Advanced Manual - 2

4 6. MODBUS ERROR CHECKING MODBUS EXCEPTIONS HARDWARE Terminal Designations Power Supply Format Setting Address Setting Baud Rate and Parity Settings PHYSICAL INTERFACE Isolated Network Non Isolated Network EXAMPLES WITHOUT COMM MEMORY Control through ASi channels Control through External Outputs Control through External Inputs EXAMPLES WITH COMM MEMORY Set outputs from local and remote Read/W rite local variables Read Analog Input / W rite Anal og Outputs AL2-MBU Advanced Manual - 3

5 1. INTRODUCTION TO MODBUS The Modbus protocol provides an industry standard method that Modbus devices use for parsing messages. This protocol was developed by Modicon Inc. for industrial automation systems and programmable controllers. Modbus devices communicate using a master-slave technique in which only one device (the master) can initiate transactions (called queries). The other devices (slaves) respond by supplying the requested data to the master, or by taking the action requested in the query. A slave is any peripheral device (PLC, I/O transducer, valve, network drive, or other devices) which processes information and sends its output to the master using Modbus. Masters can address individual slaves, or can initiate a broadcast message to all slaves. Slaves return a response to all queries addressed to them individually, but do not respond to broadcast queries. A master's query consists of a slave address (or broadcast address), a function code defining the requested action, any required data, and an error checking field. A slave's response consists of fields confirming the action taken, any data to be returned, and an error checking field. Note that the query and response both include a device address, plus a function code, plus applicable data, and an error checking field. If no error occurs, the AL2-MBU will answer within the specified AlphaXL COM TIMEOUT with the requested data (the maximum answer time: factory default = 6,6 seconds including Tw, TP and data transfer). If an error occurs in the query received, or if the slave is unable to perform the action requested, the slave will return an exception message as its response (see Modbus Exceptions). The error check field of the message frame allows the master to confirm that the contents of the message are valid. Additionally, parity checking is also applied to each transmitted character in its data frame control. AL2-MBU Advanced Manual - 4

6 MODBUS COILS AL2 LINK OUTS MODBUS COILS AL2 EXT OUTS MODBUS COILS AL2 OUTS 2. MODBUS REGISTER MAP Modbus functions operate on map registers to monitor, configure, and control I/O. Modbus registers are organized into reference types identified by the leading number of the reference address. The leading character is generally implied by the function code and omitted from the address specifier for a given function. The leading character also identifies the I/O data type. 2.1 AL2 Outputs Up to 9 channels can be read and/or set from remote, depending on the controller type. When the output channel is linked to a program Function Block it could be overwritten by the controller at further cycle O O O O O O O O O 09 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil 15 Force Multiple Coils 2.2 AL2 External Outputs Up to 4 channels can be read and/or set from remote when the boards AL2-4EYT or AL2-4EYR have been installed into the expansion slot. When the expansion output board is not installed these could be used like virtual channels EO EO EO EO 04 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil 2.3 AL2 Link Outputs Up to 4 channels can be read and/or set from remote when the board AL2-ASI-BD has been installed into the expansion slot. When the expansion output board is not installed these could be used like virtual channels AO AO AO AO 04 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil AL2-MBU Advanced Manual - 5

7 MODBUS COILS AL2 COMMUNICATION BITS 2.4 AL2 Communication Bit devices 50 or 100 Communication Bits could be optionally assigned to Communication Memory. CB are associated to any bit of FB used within the program and can be read or set from remote CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB 40 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil AL2-MBU Advanced Manual - 6

8 MODBUS COILS AL2 COMMUNICATION BITS CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB 85 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil AL2-MBU Advanced Manual - 7

9 MODBUS COILS AL2 SYSTEM BITS MODBUS COILS AL2 COMMUNICATION BITS CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB 100 Supported Modbus Functions: 01 Read Single Coil 05 Force Single Coil 2.5 AL2 System Bit Predefined system informations. Ref.: Programming Manual M M M M M M M M M M M M M M M M M M M M M M M M 24 Supported Modbus Functions: 01 Read Single Coil AL2-MBU Advanced Manual - 8

10 MODBUS COILS AL2 LINK INPUTS MODBUS COILS AL2 EXT INPUTS MODBUS COILS AL2 INPUTS 2.6 AL2 Inputs Up to 15 channels can be read from remote, depending on the controller type I I I I I I I I I I I I I I I 15 Supported Modbus Functions: 02 Read Input Status 05 Force Single Coil 2.7 AL2 External Inputs Up to 4 channels can be read from remote when the boards AL2-4EX or AL2-4EXR have been installed into the expansion slot. When the expansion output board is not installed these could be used like virtual channels EI EI EI EI 04 Supported Modbus Functions: 02 Read Input Status 05 Force Single Coil 2.8 AL2 Link Inputs Up to 4 channels can be read from remote when the board AL2-ASI-BD has been installed into the expansion slot. When the expansion output board is not installed these could be set like virtual coils E E E E 04 Supported Modbus Functions: 02 Read Input Status 05 Force Single Coil Could also be set from remote like any coil, but it will be overwritten by controller at further cycle (could make a pulse). AL2-MBU Advanced Manual - 9

11 MODBUS WORDS AL2 COMMUNICATION WORDS MODBUS WORDS AL2 ANALOG INPUTS 2.9 AL2 Analog Inputs Up to 8 channels can be read from remote, depending on the controller type AI AI AI AI AI AI AI AI 08 Supported Modbus Functions: 04 Read Input Register 2.10 AL2 Communication Word devices 50 or 100 Communication Words could be optionally assigned to Communication Memory. CW are associated to any word value of FB used within the program and can be read or set from remote CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW 28 Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register AL2-MBU Advanced Manual - 10

12 MODBUS WORDS AL2 COMMUNICATION WORDS CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW 73 Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register AL2-MBU Advanced Manual - 11

13 MODBUS WORDS AL2 COMMUNICATION WORDS CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW 100 Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register The register addresses which are not allocated to any AL2 parameter or data set are invalid. A valid answer is given if at least one of read register or coil is valid, the returned value of those parameters will be 0 (zero). An error is given when all the addressed parameters are not valid. If there is an attempt to write non allocated registers or outside the parameter addresses, the AL2-MBU gateway will return an exception code to the controller. AL2-MBU Advanced Manual - 12

14 MODBUS WORD MODBUS WORD MODBUS WORD 3. MODBUS SERIAL TRANSMISSION MODE Standard Modbus networks employ one of two types of transmission modes: ASCII Mode RTU Mode (hardware selectable on the AL2-MBU board). The transmission mode defines the bit contents of the message bytes transmitted along the network, and how the message information is to be packed into the message stream and decoded. Some configuration can be modified via the Modbus registers. 3.1 Baud Rate Default communication baud rate is New parameters are applied at next power-on : : : : : : : : BAUD RATE (kbit/s) Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register 3.2 Parity Default communication parity is NONE. New parameters are applied at next power-on : NONE 1 : ODD 2 : EVEN PARITY Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register 3.3 AlphaXL communication timeout Although communication timeout communicating with AlphaXL are the maximum declared on the original literature (Communication Manual 7.4), the controller may take more time to serve the process: a slave device failure could be returned in such cases. It s possible to increase the timeout up to 9 seconds both for Tw and TP. New parameters are applied at next power-on Tw 1 90 DEFAULT 35 (3,5s) TIMEOUT TP DEFAULT 1 (100ms) Supported Modbus Functions: 03 Read Holding Register 06 Preset Single Register AL2-MBU Advanced Manual - 13

15 4. MODBUS ADDRESSES The master device addresses a specific slave device by placing the 8-bit slave address in the address field of the message (RTU Mode). The address field of the message frame contains two characters (in ASCII mode), or 8 binary bits (in RTU Mode). Valid addresses are from 1-247, to be set using rotary switches on the AL2-MBU board. When the slave responds, it places its own address in this field of its response to let the master know which slave is responding. Address 0 is reserved for the broadcast address, which all slave devices on a network recognize. Some functions do not support the broadcast address. A slave device does not issue a response to a broadcast message. All data addresses in Modbus messages are referenced to 0, with the first occurrence of a data item addressed as item number zero. Further, a function code field already specifies which register group it operates on (i.e. 0x, 1x, 3x, or 4x reference addresses). For example, holding register is addressed as register 0000 in the data address field of the message. The function code that operates on this register specifies a "holding register" operation and the "4xxxx" reference group is implied. Thus, holding register is actually addressed as register 006BH (107 decimal). 5. MODBUS FUNCTIONS The following table highlights the subset of standard Modbus functions supported by the AL2- MBU gateway (the reference register addresses that the function operates on are also indicated): CODE FUNCTION REFERENCE 01 (01H) Read Coil Status 0xxxx 02 (02H) Read Input Status 1xxxx 03 (03H) Read Holding Registers 4xxxx 04 (04H) Read Input Registers 3xxxx 05 (05H) Force Single Coil 0xxxx 15 (0FH) Force Multiple Coils 0xxxx 06 (06H) Preset Single Register 4xxxx 43 (2BH) Read Device Identification MEI:01 When the slave device responds to the master, it uses the function code field to indicate either a normal (error-free) response, or that some kind of error has occurred (an exception response). The number of registers/coils returned in a single answer is limited to 64. A valid answer is given if at least one of read coil or register is valid, in such case the value returned for the invalid ones will be 0 (zero). An error is given when the whole addresses are not valid. AL2-MBU Advanced Manual - 14

16 5.1 Read Coil Status - 01 This command will read the ON/OFF status of discrete outputs or coils (0x reference addresses) in the slave. Broadcast transmission is not supported. The Read Coil Status query specifies the starting coil (output channel) and quantity of coils to be read. The Read Coil Status in the response message is packed as one coil or channel per bit of the data field. The output status is indicated as 1 for ON (conducting current), and 0 for OFF (not conducting). The LSB of the first data byte corresponds to the status of the coil addressed in the query. The other coils follow sequentially, moving toward the high order end of the byte. Unused bits of the data byte will be set to zero toward the unused high order end of the byte. The number of coils returned in a single answer is limited to 60 (8 bytes) Example This example reads the output channel status of coils 0-3 (physical coils 1-4)at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 1 01 Starting Address (H) 00 0 Starting Address (L) 00 Number of Points (H) 00 4 Number of Points (L) 04 CRC / LRC - - Note that the leading character of the 0x reference address is implied by the function code and omitted from the address specified. The starting address 0 (00H) is corresponding to coil 1 ( O01). RESPONSE FIELD VALUE (HEX) Slave address 247 F7 Function code 1 01 Byte count 1 01 Data coils 10 0A CRC / LRC - - To summarize, the status of coils 3-0 is shown as the byte value 0A hex, or binary. Coil 3 is the fifth bit from the left of this byte, and coil 0 is the LSB. The four remaining bits (toward the high-order end) are zero. Reading left to right, the output status of physical coils is ON-OFF-ON-OFF. BINARY HEX 0 A COILS AL2-MBU Advanced Manual - 15

17 5.2 Read Input Status - 02 This command will read the ON/OFF status of discrete inputs (1x reference addresses) in the slave. Broadcast transmission is not supported. The Read Input Status query specifies the starting input and quantity of points to be read. The Read Input Status in the response message is packed as one input per bit of the data field. The input status is indicated as 1 for ON (closed, powered), and 0 for OFF (open, not powered). The LSB of the first data byte corresponds to the status of the input addressed in the query. The other inputs follow sequentially, moving toward the high order end of the byte. Unused bits of the data byte will be set to zero toward the unused high order end of the byte. The number of inputs returned in a single answer is limited to 60 (8 bytes) Example This example reads the status of input channels (physical inputs 1-4) at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 1 01 Starting Address (H) Starting Address (L) 142 Number of Points (H) 00 4 Number of Points (L) 04 CRC / LRC - - Note that the leading character of the 1x reference address is implied by the function code and omitted from the address specified. The starting address 142 (8EH) is corresponding to coil 1 ( I1). RESPONSE FIELD 00 8E VALUE (HEX) Slave address 247 F7 Function code 1 01 Byte count 1 01 Data coils 10 0A CRC / LRC - - To summarize, the status of inputs is shown as the byte value 0A hex, or binary. Input 145 is the fifth bit from the left of this byte, and input 142 is the LSB. The four remaining bits (toward the high-order end) are zero. Reading left to right, the output status of physical inputs 4 1 is ON-OFF-ON-OFF. BINARY HEX 0 A INPUTS AL2-MBU Advanced Manual - 16

18 5.3 Read Holding Register - 03 Reads the binary contents of holding registers (4x reference addresses) in the slave device. Broadcast transmission is not supported. The Read Holding Registers query specifies the starting register and quantity of registers to be read. Note that registers are addressed starting at 0 (registers addressed as 0-99). The Read Holding Registers response message is packed as two bytes per register, with the binary contents right-justified in each byte. For each register, the first byte contains the high order bits and the second byte the low order bits. The number of registers returned in a single answer is limited to Example This example reads holding registers (Communication Words 6-8) at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 3 03 Starting Address (H) 0 00 Starting Address (L) 5 05 Number of Points (H) 0 00 Number of Points (L) 3 03 CRC / LRC - - Note that the leading character of the 4x reference address is implied by the function code and omitted from the address specified. The starting address 5 (05H) is corresponding to register 6 ( CW6). RESPONSE FIELD VALUE (HEX) Slave address 247 F7 Function code 3 03 Byte count 6 06 Data High (Register 40006) Data Low (Register 40006) D3 Data High (Register 40007) A Data Low (Register 40007) 14 Data High (Register 40008) Data Low (Register 40008) 00 CRC / LRC - - To summarize our example: the contents of register (2 bytes) is the Communication Word 6 = (00D3H); the contents of register (2 bytes) is the Communication Word 7 = (A014H); the contents of register (2 bytes) is the Communication Word 8 = 1024 (0400H). AL2-MBU Advanced Manual - 17

19 5.4 Read Input Registers - 04 This command will read the binary contents of input registers (3x reference addresses) in the slave device. Broadcast transmission is not supported. The Read Input Registers query specifies the starting register and quantity of registers to be read. The Read Input Registers response message is packed as two bytes per register, with the binary contents right-justified in each byte. For each register, the first byte contains the high order bits and the second byte the low order bits. The number of registers returned in a single answer is limited to Example This example reads input registers & (Analog Inputs 3 & 4) at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 4 04 Starting Address (H) 0 00 Starting Address (L) 2 02 Number of Points (H) 0 00 Number of Points (L) 2 02 CRC / LRC - - Note that the leading character of the 3x reference address is implied by the function code and omitted from the address specified. The starting address 2 (02H) is corresponding to register 3 ( AI03). RESPONSE FIELD VALUE (HEX) Slave address 247 F7 Function code 4 04 Byte count 4 04 Data High (Register 30003) Data Low (Register 30003) D3 Data High (Register 30004) Data Low (Register 30004) 88 CRC / LRC - - To summarize our example: the contents of register (2 bytes) is the Analog Input 3 = 211 (00D3H); the contents of register (2 bytes) is the Analog Input 4 = 136 (0088H); AL2-MBU Advanced Manual - 18

20 5.5 Force Single Coil - 05 Forces a single coil/output (0x reference address) to either ON or OFF. With broadcast transmission (address 0), it forces the same coil in all networked slaves. The Force Single Coil query specifies the coil reference address to be forced, and the state to force it to. The ON/OFF state is indicated via a constant in the query data field. A value of FF00H forces the coil to be turned ON (i.e. the corresponding relay is turned ON or closed), and 0000H forces the coil to be turned OFF (i.e. the output relay is turned OFF or opened). All other values are invalid and will not affect the coil Example This example forces discrete output 3 ON (physical output 4) at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 5 05 Starting Address (H) 0 00 Starting Address (L) 3 03 Force Data (H) 255 FF Force Data (L) 0 00 CRC / LRC - - Note that the leading character of the 0x reference address is implied by the function code and omitted from the address specified. The starting address 3 (03H) is corresponding to coil 4 ( O04). The Force Single Coil response message is simply an echo (copy) of the query as shown above, but returned after executing the force coil command. No response is returned to broadcast queries from a master device. The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the coil. The coil will remain forced if it is not programmed in the controller s logic. AL2-MBU Advanced Manual - 19

21 5.6 Force Multiple Coils - 15 Forces each coil/output (0x reference address) in a sequence of coils/outputs to either ON or OFF. With broadcast transmission (address 0), it forces the same coils in all networked slaves. The Force Multiple Coils query specifies the coil reference address to be forced, and the state to force it to. The ON/OFF state is indicated in the Force Data fields. A value of FF00H forces the coil to be turned ON (i.e. the corresponding relay is turned ON or closed), and 0000H forces the coil to be turned OFF (i.e. the output relay is turned OFF or opened). All other values are invalid and will not affect the coil Example This example forces ON all discrete outputs from 0 to 9 at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 15 0F Starting Address (H) 0 00 Starting Addre ss (L) 0 00 Quantity of Coils (H) 0 00 Quantity of Coils (L) 9 09 Byte count 2 02 Force Data (H) 255 FF Force Data (L) 1 01 CRC / LRC - - Note that the leading character of the 0x reference address is implied by the function code and omitted from the address specified. The starting address 0 (00H) is corresponding to coil 0 ( O01). RESPONSE FIELD VALUE (HEX) Slave address 247 F7 Function code 15 0F Starting Address (H) 0 00 Starting Address (L) 0 00 Quantity of Coils (H) 0 00 Quantity of Coils (L) 9 09 CRC / LRC - - No response is returned to broadcast queries from a master device. The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the coil. The coil will remain forced if it is not programmed in the controller s logic. AL2-MBU Advanced Manual - 20

22 5.7 Preset Single Register - 06 Presets a single holding register (4x reference addresses) to a specific value. When broadcast, the function presets the same register reference in all attached slaves. The Preset Single Register query specifies the register reference address to be preset, and the preset value Example This example writes the value into Register 1 (Communication Word 1) at slave 247. QUERY FIELD VALUE (HEX) Slave address 247 F7 Function code 6 06 Starting Address (H) 0 00 Starting Address (L) 1 01 Preset Data (H) Preset Data (L) 00 CRC / LRC - - Note that the leading character of the 4x reference address is implied by the function code and omitted from the address specified. The starting address 0 (00H) is corresponding to register 1 ( CW1). The Preset Single Register response message is simply an echo (copy) of the query as shown above, but is returned after the register contents have been preset. No response is returned to broadcast queries from a master device. The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the register. The register will remain unchanged if it is not written by controller s logic. AL2-MBU Advanced Manual - 21

23 5.8 Device Identification This function code allows reading the identification and additional information relative to the physical and functional description of a remote device. The Read Device Identification interface is modeled as an address space composed of a set of addressable data elements. The data elements are called objects and an object Id identifies them Categories of objects The interface consists of 3 categories of objects : Basic Device Identification. Objects of this category are mandatory: VendorName, Product code and revision number Regular Device Identification. In addition to Basic data objects, the device provides additional and optional identification and description data objects. All of the objects of this category are defined in the standard but their implementation is optional Extended Device Identification. In addition to regular data objects, the device provides additional and optional identification and description private data. All of these data are device dependent Identification request A Modbus Encapsulated Interface (MEI) assigned number 14 identifies the Read identification request. Four access types are defined : 01 : request to get the basic device identification (stream access) 02 : request to get the regular device identification (stream access) 03 : request to get the extended device identification (stream access) 04 : request to get one specific identification object (individual access) Example of a Read Device Identification request for "Basic device dentification" of AL2-MBU. In this example all information are sent in one response PDU (only Basic Device Idetification, MEI=01 supported). REQUEST RESPONSE Field Name Value Field Name Value Function 2B Function 2B MEI Type 0E MEI Type 0E Read Dev Id Code 01 Read Dev Id Code 01 Object Id 00 Conformity Level 01 More Follows 00 Next ObjectId 00 Number of Objects 03 Object Id 00 Object Length MAUFACTURER Object Value CONTRIVE ITALY 0E Object Id 01 Object Length 07 DEVICE TYPE Object Value AL2-MBU Object Id 03 Object Length 08 FIRMWARE VERSION Object Value AL2-MBU Advanced Manual - 22

24 6. MODBUS ERROR CHECKING Modbus networks employ two methods of error checking: parity checking of the data character frame Even, odd, or no parity frame checking within the message frame Cyclical Redundancy Check in RTU Mode, Longitudinal Redundancy Check in ASCII Mode 7. MODBUS EXCEPTIONS In a normal response, the slave echoes the function code of the original query in the function field of the response. All function codes have their most-significant bit (msb) set to 0 (their values are below 80H). In an exception response, the slave sets the MSB of the function code to 1 in the returned response (i.e. exactly 80H higher than normal) and returns the exception code in the data field. This is used by the master's application to recognize an exception response and to direct an examination of the data field for the applicable exception code. CODE EXCEPTION DESCRIPTION 01 Illegal Function The function code received in the query is not allowed or invalid. 02 Illegal Data Address The data address received in the query is not an allowable address for the slave or is invalid. 03 Illegal Data Value A value contained in the query data field is not an allowable value for the slave or is invalid. 04 Slave Device Failure An unrecoverable error occurred while the slave was attempting to perform the requested action. The master's application program must handle the exception response. It may choose to post subsequent retries of the original message, it may try sending a diagnostic query, or it may simply notify the operator of the exception error. AL2-MBU Advanced Manual - 23

25 8. HARDWARE The AL2-MBU Modbus Gateway module is an optional device for Mitsubishi 2 controllers which enables the connection to a Modbus system. The 2 controller is considered as a slave on the Modbus network. Before attempting to use AL2-MBU, the following original MITSUBISHI manuals should be carefully read and understood: Hardware Manual Programming Manual Software Manual Communication Manual For any information on 2 controller and its derivate products, please refer to the literature provided by MITSUBISHI and available for download at: Terminal Designations A Data negative (Conductor 1 in twisted pair). B Data positive (Conductor 2 in twisted pair). - Ground (Conductor 3 in a three-wire system) and negative power supply + Positive power supply Data line B is positive with respect to data line A when ALl2-MBU is transmitting Power Supply The logic side of the gateway is powered from the 2 controller side. An external power supply must be provided for the bus side. Although it s possible to supply the bus side using the same 24V used for the controller, it s strongly suggested to provide an independent power supply. This independent supply must be externally protected. Each AL2-MBU will draw 2,5mA from the bus in idle mode, rising to a max of 150mA while in transmission mode. 8.2 Format Setting The AL2-MBU supports both the RTU and ASCII protocol. Leave the jumper open to operate RTU mode, close the jumper for ASCII mode. A valid selection is applied on power up. This cannot be modified during operation. AL2-MBU Advanced Manual - 24

26 8.3 Address Setting The address is set using two rotary encoding switches. The left switch is used to set the most significant character and the right switch is used to set the least significant character. Addresses can be set between 1 and 247 in hexadecimal format ranging 00 to FF. Address 0 is reserved for the broadcast address, which all slave devices on a network recognize. The figure below shows the address setting "14". Any address change will take place immediately, also when the unit is running. 8.4 Baud Rate and Parity Settings In addition to the described setting options, some configuration can be modified via the Modbus registers. Default communication baud rate is 9600, edit Modbus Register to modify. Default parity option is NONE, edit Modbus Rgister to modify. The new parameters are applied at next power-on. AL2-MBU operates with factory default settings for 2 controller: OTHER COM, 8 bits data length, No parity, 1 stop bit, STATION NUMBER = 0. Parameters can be modified through local keyboard or VLS software. AL2-MBU Advanced Manual - 25

27 9. PHYSICAL INTERFACE Modbus is a serial, asynchronous protocol. The Modbus protocol does not specify the physical interface. Typical physical interfaces are RS-232 and RS-485. AL2-MBU gateway provides a galvanically-isolated ANSI EIA/TIA-485-A interface, designed for bidirectional data communication on balanced, multipoint bus transmission lines and is slewlimited to reduce reflections with improperly terminated lines. It's a fractional (1/8) power transceiver, allowing up to 256 similar transceivers on the bus. Building mixed network with classic full power transceiver, a line repeater must be provided for each group of 32 units. The receiver inputs have a true fail-safe feature that ensures a reliable operation when the inputs are open or shorted. Current limiting and thermal shutdown features protect against output short circuits and bus contention situations that might cause excessive power dissipation. Use shielded twisted-pair wire to connect each slave to the Modbus network, daisy-chain style. The polarity of the twisted pair is critically important. Close the jumper for the built-in bus termination if the AL2-MBU is installed at the end of the bus, otherwise the bus termination jumper must be left open. Bus termination prevents signal reflections from the bus cable ends. Multiple controllers can be networked together using AL2-MBU. A maximum of 247 controllers can be connected together. Max wiring distance should not exceed 1200 m (4000 ft.) at 19,200 baud. THE SHIELD SHOULD BE GROUNDED IN ONE PLACE ONLY Grounding the shield at multiple points will create a ground loop that may disrupt communications or cause damage to the controller circuitry. AL2-MBU Advanced Manual - 26

28 9.1 Isolated Network Figure below illustrates a typical configuration where three slave units are shown. The communication wires are daisy-chained from one controller RS-485 port to the next. Power for bus side of AL2-MBU is supplied by a power supply unit. Of course it s possible to provide different power supplies for each AL2-MBU gateway or group of AL2-MBU gateways but the negative must be linked to reference ground. Termination must be activated at the last AL2-MBU of the network. Termination must be provided also at the first unit of the network (usually the master). Negative power supply must be used like RS-485 reference ground, three-wire connection is highly recommended as it improves noise immunity. AL2-MBU Advanced Manual - 27

29 9.2 Non Isolated Network Figure below illustrates a typical configuration where three slave units are shown. The communication wires are daisy-chained from one controller RS-485 port to the next. Power for bus side of AL2-MBU is supplied from the same power supply of 2 controller. Termination must be activated at the last AL2-MBU of the network. Termination must be provided also at the first unit of the network (usually the master). Negative power supply must be used like RS-485 reference ground, three-wire connection is highly recommended as it improves noise immunity. AL2-MBU Advanced Manual - 28

30 6. EXAMPLES WITHOUT COMM MEMORY It s possible to control some I/Os from remote through Modbus within a FB program without Communication Memory allocation. 6.1 Control through ASi channels In the figure below ASi channels are user within a program and can be read / set from remote. This can be done also when AL2-ASI-BD is not installed into 2, allowing a remote control through virtual channels (without assigning communication memory). MODBUS 2 SIGNAL MODE O02 Motor (direct) READ / SET O03 Heather (direct) READ / SET O05 Clutch (direct) READ / SET A01 Position sensor (through LinkIN) READ A02 Counter clear push button (latched) READ I01 Position sensor (direct) READ I06 Counter clear push button READ / SET E01 Heather Output enable READ / SET E02 Counter pulse generator READ / SET E03 Reset Clear counter latch READ / SET AL2-MBU Advanced Manual - 29

31 6.2 Control through External Outputs In the figure below the status of an External Outputs is read from remote. This can be done also when AL2-4EYx is not installed into 2, allowing a remote control through virtual channels (without assigning communication memory). MODBUS 2 SIGNAL MODE I01 Alarm test pushbutton READ I06 Door limit switch (direct) READ I08 Acknowledge push button READ / SET O01 Visual alarm (direct) SET O01 Audible alarm (direct) SET EO01 Door limit switch (latched) READ The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the register. The register will remain unchanged if it is not written by controller s logic. AL2-MBU Advanced Manual - 30

32 6.3 Control through External Inputs In the figure below the status of an External Outputs is read from remote. This can be done also when AL2-4EX is not installed into 2, allowing a remote control through virtual channels (without assigning communication memory). MODBUS 2 SIGNAL MODE O04 Motor (direct) READ / SET EI01 Run Motor READ / SET EI02 Stop Motor READ / SET O06 Heather (direct) READ / SET AL2-MBU Advanced Manual - 31

33 7. EXAMPLES WITH COMM MEMORY Some digital and analog variables used within a program can be assigned to Communication Memory, to be set and read from remote through Modbus interface. Ref.: α2 SIMPLE APPLICATION CONTROLLER COMMUNICATION MANUAL 6 Ref.: α2 SIMPLE APPLICATION CONTROLLER SOFTWARE MANUAL Set outputs from local and remote A simple remote control of outputs leaving local control can be achieved using SET/RESET FB. Set and Reset inputs can be left unconnected if the control is achieved only from remote. The output could be set retentive (after power-off). MODBUS 2 SIGNAL MODE I01 Set output 2 READ / SET I05 Reset both outputs READ / SET CB1 B01 - Output on (resetable) READ / SET CB2 B02 - Output on (resetable) READ / SET O02 Output 2 (direct) READ / SET O04 Output 4 (direct) READ / SET AL2-MBU Advanced Manual - 32

34 The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the register. The register will remain unchanged if it is not written by controller s logic. To assign CB (Communication Bits) select Dedicated Communication from Option menu: Depending on Communication Memory settings, 50 or 100 Bit Devices will be allocated. Select Bit Device tag. Leave Station = 0. Select from the left column the FB Bit Devices to be shared with Modbus Choose the CBNo from Communication Bit Device table Click the Set button Repeat until all association are completed B01 - Set Reset Output 2 CB1 available from Modbus at coil B02 - Set Reset Output 4 CB2 available from Modbus at coil WARNING When the controller is running, most of digital variables are written directly by the program thus remote setting could be overwritten. AL2-MBU Advanced Manual - 33

35 7.2 Read/Write local variables Complete interactivity can be achieved assigning local variables to Communication Memory. In the example above a position switch will enable the PWM generator that can be set from remote. Selected motor speed value is reported on the local display. A tacho sensor will read the real motor speed, the value is reported on the local display and can be read from remote. Output 5 will turn on exceeding speed limits, that can be set from remote. MODBUS 2 SIGNAL MODE I02 Position switch READ / SET I06 Tacho sensor READ / SET CB1 B05 - Speed Control Output READ / SET CW1 B04 - Speed setting READ / SET CW2 B05 - Pulse period READ / SET CW3 B05 - Pulse current period READ / SET O03 Output 3 (direct) READ / SET O05 Output 5 (direct) READ / SET The function will override the controller s settings. The forced state will remain valid until the controller s logic next solves the register. The register will remain unchanged if it is not written by controller s logic. AL2-MBU Advanced Manual - 34

36 To assign CB (Communication Bits) select Dedicated Communication from Option menu: Depending on Communication Memory settings, 50 or 100 Bit Devices will be allocated. Select Bit Device tag. Leave Station = 0. Select from the left column the FB Bit Devices to be shared with Modbus Choose the CBNo from Communication Bit Device table Click the Set button Repeat until all association are completed B05 Speed Detect Output CB1 available from Modbus at coil WARNING When the controller is running, most of digital variables are written directly by the program thus remote setting could be overwritten. AL2-MBU Advanced Manual - 35

37 To assign CW (Communication Words) select Dedicated Communication from Option menu: Depending on Communication Memory settings 50 or 100 Word Devices will be allocated. Select Word Device tag. Leave Station = 0. Select from the left column the FB Word to be shared with Modbus Choose the CWNo from Communication Word Device table Click the Set button Repeat until all association are completed B04 Speed CW1 available from Modbus at coil B05 Pulse Period CW2 available from Modbus at coil B05 Pulse CurPeriod CW3 available from Modbus at coil WARNING When the controller is running, most of digital variables are written directly by the program thus remote setting could be overwritten. AL2-MBU Advanced Manual - 36

38 7.3 Read Analog Input / Write Analog Outputs Analog inputs can be read directly. Assign variables to Communication Memory to read modified values or set analog outputs (AL2-2DA installed: MODBUS 2 SIGNAL MODE AI V Setpoint READ AI V Temperature READ CW1 B05 - Scaled Setpoint READ / SET CW2 B10 - Scaled Temperature READ / SET CW3 B07 Value for Analog Output B03 READ / SET CW4 B08 Value for Analog Output B09 READ / SET Two dummy Function blocks can be used to transfer value to ANALOG OUTPUTS: B07 ONE SHOT range B08 ADD range input must be forced to ground Analog outputs can accept values in the range (max 4040) to be converted to (max 10.1) V (max 2020) to be converted to (max 20.16) ma AL2-MBU Advanced Manual - 37

39 To assign CW (Communication Words) select Dedicated Communication from Option menu: Depending on Communication Memory settings 50 or 100 Word Devices will be allocated. Select Word Device tag. Leave Station = 0. Select from the left column the FB Word to be shared with Modbus Choose the CWNo from Communication Word Device table Click the Set button Repeat until all association are completed B05 GainAnalogVal CW1 available from Modbus at coil B10 GainAnalogVal CW2 available from Modbus at coil B07 SetOneShot CW3 available from Modbus at coil B08 Sum CW4 available from Modbus at coil WARNING When the controller is running, most of digital variables are written directly by the program thus remote setting could be overwritten. AL2-MBU Advanced Manual - 38

40 AL2-MBU Advanced Manual - 39