RCF DMA 82 User manual

OWNER’S MANUAL
MANUALE UTENTE
DMA AMPLIFIERS SERIES
Third parties control protocol
Protocollo di controllo terze parti

3
CONTENTS
ENGLISH ...................................................................................................................................................... 4
SYSTEM ARCHITECTURE ........................................................................................................................... 4
TECHNICAL SPECIFICATIONS .................................................................................................................... 6
COMMUNICATION FRAME DESCRIPTION ................................................................................................. 7
REGISTRATION SEQUENCE ..................................................................................................................... 10
PROTOCOL COMMANDS ........................................................................................................................ 14
DMA 82 / DMA 162 COMMANDS ........................................................................................................... 17
DMA 162P COMMANDS ......................................................................................................................... 22
ITALIANO ................................................................................................................................................... 26
ARCHITETTURA DEL SISTEMA ................................................................................................................. 26
SPECIFICHE TECNICHE ............................................................................................................................ 28
DESCRIZIONE DEL FRAME DI COMUNICAZIONE ..................................................................................... 28
SEQUENZA DI REGISTRAZIONE ............................................................................................................... 32
COMANDI DI PROTOCOLLO .................................................................................................................... 36
COMANDI DMA 82 / DMA 162 ............................................................................................................... 3
COMANDI DMA 162P ............................................................................................................................. 44

4
ENGLISH
SYSTEM ARCHITECTURE
In order to control the DMA series amplifiers through the communication protocol, the following devices are
required:
1. a PC <> RS485 converter, for example usb <> RS485;
2. an RS485 <> RDNET converter (on RJ45 connector). This device shall map on the RS485 connector (for
example DB- ) the pinout necessary to communicate with the DMA device via RDNet protocol. The pinout
is described in the table below:
3. a RDNET BOARD DMA accessory (pn 123 048) for each device to be controlled.
It is now possible to proceed with the following architecture.
Up to 32 devices can be connected, regardless of the model.

5
Note
Through this architecture it is possible to control only the devices connected via the RDNET BOARD DMA
accessory, and therefore it is not possible to control the devices connected via BUS, as shown in the following
figure.

6
TECHNICAL SPECIFICATIONS
The main technical characteristics of the communication network are listed in the table below.
Status refresh rate 5 Hz ÷ 10 Hz
Data rate 115.2 kbit/s
Cyclic redundancy check CRC-16
Serial transmission 8 bit
No parity
1 stop
Bus maximum length 600 m (optimum)
1000 m (maximum)
Physical layer of communication between central and remote units EIA-485
Dynamic assignment of addresses to remote units SI
Addressing mode Unicast/Broadcast
SYSTEM REQUIREMENTS
Firmware version DMA 82
DMA 162
2.
DMA 162P 1.8

7
COMMUNICATION FRAME DESCRIPTION
The communication frame is made of a sequence of bytes ordered as follows:
The message frame begins with the STX symbol and ends with the ETX symbol. In this way, if the destination
loses the boundaries of a frame, regains it when the next STX and ETX pair arrive.
However, there is a problem: in the transmission of binary data, the byte corresponding to the STX and ETX
encoding can appear inside the frame, introducing confusion. To avoid this, the byte stuffing technique is
used.
The above mentioned symbols are made up of copies of bytes all starting with the first byte 0X02 which acts
as escape symbol.
STX and ETX symbols and DATA = 0x02 are encoded with the following bytes couple:
STX (0x02, 0x02) Start transmission
ETX (0x02, 0x03) Stop transmission
DATA 0x02 (0x02, 0x00) Generic 0x02 character
All other values are specified by their value in a single byte:
DATA = 0x00 ÷ 0x01 ÷ 0x00 ÷ 0x01
DATA = 0x03 ÷ 0xFF ÷ 0x03 ÷ 0xFF
After the STX field follows the ADDR field which identifies the remote slave unit. The range of slave addresses
varies from 1 to 255. The master addresses a slave by entering the slave address in the ADDR field of the
message. When the slave node returns its response, it enters its address in the ADDR field of the message to
inform the master which slave it is responding to.

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The range of addresses is divided as follows:
•The ADDR = 0x00 address corresponds to the default address of each slave.
•The address ADDR = 0XFF is reserved for broadcast messages that all slaves recognize.
After the ADDR field the LENGTH field comes which indicates the length in bytes of the DATA field.
The CMD field is used to indicate to the slave the type of action to be taken. This field uses 2 bytes and the
range of codes varies from 0 to 65535.
The CMD field can be followed by the DATA field which contains the request and/or response data.
The CRC field or the Cyclic Redund ncy Code contains the result of the redundancy check calculated on the
transmitted message
The communication frame is therefore composed of the following bytes sequence:
STX[0] 0x02 START FRAME
STX[1] 0x02 START FRAME
ADDR 0x00 ÷ 0xFF Slave address
LENGTH 0x00 ÷ 0xFF Length in bytes of the DATA queue
CMD H 0x00 ÷ 0xFF Command to be executed MSByte
CMD L 0x00 ÷ 0xFF Command to be executed LSByte
DATA 0x00 ÷ 0xFF DATA queue
" " "
" " "
DATA 0x00 ÷ 0xFF DATA queue
CRC H 0x00 ÷ 0xFF CRC16 MSByte
CRC L 0x00 ÷ 0xFF CRC16 LSByte
ETX[0] 0x02 END FRAME
ETX[0] 0x03 END FRAME
The length of the frames is variable and is fixed at a maximum of 256 bytes. The payload for each communication
frame is 8 bytes.
When the slave responds to the master, it uses the CMD to indicate both a correct response and a response to
an error that has occurred (exception response). For a simple acknowledge response, the slave simply echoes
the original CMD.

In the event of no response or incorrect response (mismatched control codes), the master makes some attempts
to interrogate the same slave. The master can easily discriminate the type of response from the length, in fact:
no data implies a positive response, a length equal to 1 identifies an error, otherwise the data relating to the
query are reported.
CRC-16 CALCULATION
The CRC (Cyclic Redundancy Check) is made up of two bytes and is calculated by the transmitting device (both
MASTER and SLAVE) which postpones it to the message. The receiving device recalculates the CRC when
receiving the message and compares this value with the one received. If the two values are different, an error
is reported.
The calculation of the CRC is started by preloading a 16-bit register with all bits at 1. Then the calculation of
the CRC proceeds by inserting the bytes of the message to the current contents of the register. Only the 8 least
significant bits in each character are used for CRC generation. The start (STX) and stop (ETX) characters do not
apply for the CRC calculation.
During the CRC generation, an exclusive OR (XOR) logic operation is performed between each 8-bit character
and the contents of the register.
Then the result is translated (shift operation) in the direction of the least significant bit (LSB) with an insertion
of zero (zero filling) in the position of the most significant bit (MSB). The bit extracted in this way is then
examined. If it is 1 then an XOR operation is performed between the contents of the register and a
predetermined value which depends on the generator polynomial used. If it is 0, no XOR operation is performed.
The process is repeated until 8 translations of the register contents are made. Therefore a new character can be
inserted in the register with an XOR operation between the character itself and the present content of the
register.
The final content of the register, after all the characters of the message have been entered, is the CRC value.
The procedure for generating the CRC-16, used in the protocol, is summarized as follows:
1. Initialize a 16-bit register with the value 0xFFFF. This register is called the CRC register.
2. Execute the XOR operation in the CRC register between the first 8-bits of the message and the least
significant byte of the register itself.
3. Left shift the CRC register by one bit, filling the most significant bit with zero.
4. If the extracted bit is zero, repeat point 3. If the extracted bit is one, execute the XOR operation between
the contents of the register and the value 0xA001 which corresponds to the use of a generator polynomial
x
16
+ x
15
+ x
2
+ 1.
5. Repeat steps 3. and 4. until 8 translations have been performed to complete the CRC of the current byte
of the message.
6. Repeat steps 2. to 5. for all subsequent bytes of the message.
7. The final content of the register is the CRC of the message.

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REGISTRATION SEQUENCE
To be able to logically distinguish the slaves from each other, it is necessary to assign a unique address to each
node connected on the line. This assignment is made dynamically during the bus start-up phase.
Sequentially, starting from the remote unit physically closest to the master, an address is assigned for each slave.
In this way the master gets the arrangement of the remote units, knowing their relative position.
When the system is turned on, the Slave units have their own bus isolation relay in the open position. In this
configuration the slave units do not propagate the signal from the input communication connector to the output
communication connector and only the first slave unit is connected to the line and correctly terminated.