https//www.racom.eu/eng/support/protocols_docum/bc261a_modbus.html
1. INTRODUCTION
The MODBUS protocol in its standard format contains one Master and a group of
Slaves connected by an RS485 bus network. There can be a maximum of 255 Slaves -
single-byte address). The Master cyclically polls individual Slaves and reads data
from them. Mingled in with this are commands which the Master inserts between
requests as is necessary. Each frame from the Master is either duly confirmed or
contains data corresponding to the function of the frame. The Master does not have
its own address.
Modbus network with RS485 bus:
master slave
PLC PLC ___
| | | addresses:
______ +-------------------|___| 01
| | | ___
| PLC |--------------+ | |
|______| +-------------------|___| 02
| ___
|RS485 | | 03
+-------------------|___|
|
In the following diagram the Modbus network is connected by the MORSE radio
network. Slave PLC's are connected separately or in groups to the MORSE CU
(communication unit, modem, radio), which locally substitutes the function of the
Master PLC:
master Radioslave Radiomaster slave
PLC CU CU PLC
______ \|/........... \|/
| |RS232 _|_ : _|_ ___ slave
| PLC |-----| | : | | RS485 | | addresses:
|______| |___| : |___|-----+---|___| (0):01
(m)ode:Radioslave :(m):Radiomaster| ___
(f)irst: 691122FF : 69112201 | | |
Modbus (a)ddress:FF : +---|___| (1):02
:
:..... \|/
: _|_ ___
: | | RS485 | | (0):03
: |___|----+----|___|
: 69112203 | ___
: | | |
: +----|___| (1):04
:..... \|/
_|_ ___
| | RS232 | |
|___|---------|___| (0):05
69112205
period net (t)x TO (p)eriod
mirror (t)imeout
The Modbus is interrupted by the inserted radio network which mediates the
connection in the three modes described below. Radioslave (RS) and Radiomaster (RM)
are the CU with Modbus protocol.
The Modbus address of the Radioslave is the same as the lower byte of it's MORSE
address. The lower byte of the address of CU Radiomaster is the same as one of the
addresses of the connected PLC slaves. For routing other PLC´s the
"multiaddressing" function in menu "Ne" is used.
Symbols in brackets such as "(p)eriod" label protocol parameters. An example of
addresses is also given.
The MODBUS protocol for MORSE can operate in three modes:
- transparent, cache and packet:
Transparent mode.
All packets arriving from the Master PLC to the Radioslave CU are immediately sent
through the MORSE network to the respective remote Radiomaster CU and transferred
to the Slave PLC. The packet must contain the Slave address in the first byte and
the number of the Modbus function in the second, then data and finally the CRC.
The packet passes through the protokol and the MORSE network without change. A
message is only accepted from the Slave PLC as a reply to a inquiry and is sent to
the inquirer´s address. The mode is only suitable for small networks with a longer
Master - Slave inquiry interval.
Cache mode.
The Radiomaster CU polls the connected Slave PLC in a short interval "(p)eriod" and
stores obtained data in its cache memory. Only when there is a change in data in
this memory is a packet sent through the MORSE network to the Radioslave CU. This
maintains data from all Slave PLCs connected via the MORSE network in its memory.
Upon an inquiry which is made with a short period it transfer data to the Master
PLC. Transfer of commands from the Master to the Slave, which is less frequent, is
done in transparent mode.
Cache mode only transfers data changes (+ refresh over a longer time interval)
through the MORSE network, which is why it is suitable for larger networks. The
Slave can only transmit as a reply to a received command; direct Slave - Slave
communication is not possible.
Packet mode.
In packet mode periodic master slave communication over RS485 or RS232 wire
links is maintained, i.e. Master PLC Radioslave, Radiomaster Slave PLC.
During this communication only a short descriptor is transferred and only in the
case of new information is the whole data buffer transferred. On the basis of
information from the data buffer the CU generates a MORSE packet which is sent
through the MORSE network to the destination CU.
The difference between the master and the slave thereby diminishes. The Slave PLC can send a
message without being polled, and even for another Slave PLC.
The Transparent and Cache modes or also the Transparent and Packet modes can
work simultaneously. The Transparent mode is often used for servicing the PLC in
these cases. All modes require that the Master is able to wait for a longer time
(seconds) for a command reply from the Slave.
2. DATA FORMAT
Overview of Modbus commands for reading and writing from various parts of the PLC
memory.
The more exactly description is in the article "Format of MODBUS frame for MORSE".
function/8 unit for PLC
(hex) number/16
read | |
| |
02 1bit | Bin |-> physical output
0F --> bits | OUT |->
|___________|->
| Analog |
04 1word | |
03 words | Registers |
17 words | |
|___________|
An overview of the formats of Modbus functions (function No., direction information
transferred, function names, size of "num" unit is 1 or 16 bits):
Master-Slave REQUEST from Master | RESPONSE from Slave
|
01 B_out
|adr/8| fce/8| start/16| 0xFF00| crc/16| =set 1 bit ON
|adr/8| fce/8| start/16| 0xFF00 |crc/16|
|adr/8| fce/8| start/16| 0x0000| crc/16| =set 1 bit OFF
|adr/8| fce/8| start/16| 0x0000 |crc/16|
06 --> H_Reg
|adr/8| fce/8| start/16| data/16| crc/16| =write 1 word
|adr/8| fce/8| start/16| data/16|crc/16|
0F --> B_out 01
|adr/8| fce/8| start/16| num/16| cnt/8| data/8*cnt| crc/16|
|adr/8| fce/8| start/16| num/16 |crc/16|
10 --> H_Reg 16
|adr/8| fce/8| start/16| num/16| cnt/8| data/16*num|crc/16|
|adr/8| fce/8| start/16| num/16 |crc/16|
17 H_Reg 16 16
|a/8 | f/8| rst/16| rno/16| wst/16| wno/16| wcnt/8| wdata/8*cnt |crc/16|
|adr/8| fce/8|cnt/8| data/cnt*8 |crc/16|
reply to the command entered incorrectly Err
|adr/8| 0x80+fce /8| excode/8| crc/16|
adr,a - address of PLC on Modbus busbar
fce,f - function which the PLC performs upon receiving a frame
start - start address of data (output) which will be processed
num - number of words (f03.04.10.17) or bits (f01.02.0F) for reading or writing
cnt - number of bytes necessary for the transfer of the requested data
data - states of read or written registers
crc - security word
rst - start of read section
rno - length of read section
wst - start of written section
wno - length of written section
wcnt - number of bytes necessary for the transfer of written data
wdata - written data
excode - number of exceptions, specifies error
1 - function number error
2 - data address error
3 - data content error
5 - acknowledged receipt of command the performance of which is slow
6 - refusal, Slave is busy executing the slow command
Example of communication:
15:28:06.780 tx 8 | S00
0403 1000 0001 809F
15:28:06.784 rx;i 7 | S00
0403 0200 0074 44
04 - respondent address
03 - reading from Holding register
1000 - from address 1000
0001 - read 1 word
809F - crc
04 - answering address
03 - reading from Holding register
02 - 2 byte read
0000 - content of read bytes
7444 - crc
3. IMPLEMENTATION IN MORSE
The mode is set in the SPe0t menu:
MODBUS parameters:
(m)ode:RADIOSLAVE (a)utomaster:OFF
(c)ache:OFF (p)acket:OFF (t)rans:ON
(M)aster (S)lave
(A)utomaster
(C)ache
(P)acket
(T)rans
(s)ervices (O)ld menu (sw ver =< 5.74)
(q)uit
>>
Modem as RADIOSLAVE:
slave parameters:
Modbus (a)ddress:FFh
(r)epeat discard:0
d(e)vice type:PLC
(q)uit
>>
The Radioslave appears in the MORSE network under an address with the same last
byte as item "Modbus (a)ddress:", e.g. 691122FF.
Communication over the link with the Master PLC is controlled from the Master. If
the Master PLC is not able to wait for the reply from the Slave via the MORSE
network and keeps sending repeated commands it is possible to set the number of
repeated inquiries that will be discarded before Radioslave will react to the other
commands using the "(r)epeat discard:" parameter. This is a measure taken against
overloading the radio network.
Modem as RADIOMASTER:
master parameters:
(f)irst:691122FFh (s)econd:00000000h destination
d(e)vice type:PLC
Modbus slave addr: (0):3h (1):4h (2):0h (3):0h
(a)ddress mask:FFh
(p)eriod:20*10 ms
(t)imeout:10*100 ms
(q)uit
>>
The Radiomaster appears in the MORSE network under an address with the same last
byte as one of "Modbus slave addr:", e.g. 69112203. It receives messages for the
others of them by means of the Multiaddressing function (in menu Ne). The address
of the respective Radioslave is given in the "(f)irst:" field. If a non-zero
address is written in the "(s)econd:" field copies of message from the Slave are
sent to it but not reports sent with a "mirror" period.
Communication over the RS485 link (or over RS232 for a single Slave) takes place
with a "(p)eriod:" period (in this case 200 ms). It waits a maximum of "(t)imeout:"
for a reply. MORSE Modbus translation of addresses is done using "(a)ddress
mask:", which has a maximum of 8 bits.
3.1. TRANSPARENT MODE
transparent parameters:
CRC (a)uto:OFF
check (f)unction:ON
check a(d)dress:ON
check (C)RC:ON
(q)uit
>>
In transparent mode all data from the Master to the Slave is transferred through
the network. It is used for the transfer of executing commands from the Master in
Cache mode. For bi-directional transfer the transparent mode is suitable for very
small networks with slow polling cycles. Checks are used in RM for restricting the
transfer of spurious packets:
check (f)unction:ON - the function must be one of the range 1.2,3.4,5.6,F,10.17.1E
check a(d)dress:ON - the address must be one of the addresses
in the menu SPe0tM0.1,2.3,
i.e. one of the addresses of the connected Slave PLCs
check (C)RC:ON - correctness of crc for MORSE -> Modbus direction
In the Radioslave CU we use (f)unction and (C)RC checks. An address check is not
used. It is only possible to use it when there are not more than 4 Slave stations.
Then these addresses have to be written into menu SPe0tM0.1,2.3 in the Radioslave
and the function "check a(d)dress:" uses them for checking addresses.
The function "CRC (a)uto:" used in the Radiomaster CU adds a crc to packets coming
from MORSE to Modbus. It is only used for testing purposes.
After sending a packet to the Slave the Radiomaster expects a reply from the Slave,
within a max. period of SPe0tMt (=timeout), which it then sends through the MORSE
network to the Radioslave.
3.2. PACKET MODE
In packet mode two memory buffers are created in each PLC and in modems for the
transfer of data from Slave->Radiomaster (host to net, H2N) and back (net to host,
N2H). Buffers have a min. length of 250 byte (max. length of Modbus frame), and a
max. length of 1600 byte (max. length of MORSE packet).
The Radiomaster periodically asks each Slave for the content of the first word of
the H2N buffer called the descriptor. If it is a non-zero value the length of the
pseudoframe prepared in H2N is determined from it and this is then transferred to
the Radiomaster during the next communication. The descriptor is then deleted,
which is an indication for the Slave of the possibility of transferring another
frame.
Transfer from the Radiomaster (RM) to the Slave occurs in such a way that the RM
reads the N2Hdesc descriptor in the Slave PLC and if it is zero it writes its
pseudoframe into N2H. After processing it the Slave writes a zero word into N2Hdesc
indicating that the N2H buffer is again available.
The H2Nfr and N2Hfr pseudoframes have a header 6 bytes in length, data and a crc.
The header contains the necessary data for creating a MORSE packet and sending it
to the Radioslave or another Radiomaster.
Structure of buffers:
H2Nbuf:
| H2Ndesc/16 | H2Nfr/modbusMRU |
N2Hbuf:
| N2Hdesc/16 | N2Hfr/modbusMTU |
description of individual items:
H2Ndesc -
stands for "host to net descriptor", and contains information necessary for
transferring the packet via the Modbus:
H2Ndesc: |ret/1|rep/1|No/2|res/1|rxsize/11|
N2Hdesc: |ret/1|rep/1|No/2|res/1|txsize/11|
ret - 0 - user pseudoframe,
1 - routing pseudoframe (reserved for Racom use)
rep - repeat bit
No - packet number
res - reserved, should be zero
rxsize,txsize - size of pseudoframe including address and type in bytes
H2Nfr - user pseudoframe
N2Hfr - user pseudoframe
modbusMRU - Maximum Receive Unit
modbusMTU - Maximum Transmit Unit
Memory addresses of individual blocks (H2N, N2H) are freely configurable in the
modem according to the needs of the connected device. The pseudoframe contains the
actual packet determined for transfer to/from the network. A header containing
network information is concealed inside the pseudoframe. The header is located
immediately behind the descriptor in the buffer. The structure of header and data
of the pseudoframe is as follows:
User pseudoframe:
| T/8 | D/1 | R/4 | N/3 | A/32 | data |
T - type of packet
D - bit DTE, if it is 0, the sender is DCE, A is source address
conversely if it is 1, the sender is DTE, A is destination address
R - reserved, must be zero
N - network number (transmitted along the network).
A - address in the network
data - actual data of the pseudoframe
A Radiomaster, which services several (max. 4) Slaves, uses Multiaddressing. This
determines that packets from the MORSE network, determined for some of its Slaves,
are accepted by the Radiomaster and that they leave its user port for SCC with
Modbus.
Slave Modbus address are created from MORSE addresses by masking. The last byte of
the address is used. We write FF mask into field "SPe0tMa" in the parameters.
Packet mode also enables the translation of address between MORSE and Modbus using
Art tables designated by parameter "SPe0tPA". The Art table must contain the
addresses of all Slaves connected to the Radiomaster. E.g. RM 69112205 has Slave 01
and 02 connected:
dest: gw:
69112205 00000001
69112206 00000002
We can switch on table Art transfer in the Radiomaster with parameter "SPe0tA1".
We switch Multiaddressing on with: "Ne1MLn", "Ne1l1", "Tl1p6 n5".
3.3. CACHE MODE
CACHE mode is used for the collection of data from a larger number of Slave PLCs.
It complements Transparent mode for the transfer of (less frequent) commands in the
Master -> Slave direction.
In cache mode similar memory space - cache - is created in PLCs and in modems as in
packet mode. Data is transferred from Slave -> RM over wires with a short period
"SPe0tMp" selected in the 50 to 100ms range. This maintains an up-to-date image of
the state of connected Slaves in RM. If there are no changes in this image it is
sent via radio to RS in "SPe0tCt" intervals. If a change occurs in RM cache the
message for RS is sent immediately. This is how up-to-date images of the cache of
all connected Slaves are maintained in RS cache with minimum loading of the radio
network. The Master PLC then reads this cache in RS the same as if it would read
the states of all Slaves via the Modbus network.
When monitoring the state of cache memory the whole content of cache is transferred
over the link (in packet mode only the descriptor is transferred). Polling is
controlled by the Radiomaster or Master PLC (the same as in packet mode).
Information is only transferred in the Slave -> Master direction (in packet mode it
is in both directions and also between Slaves).
We define memory blocks for the cache function the same way in RS and RM using Art
table "SPe0tCc". A max. of 4 cache memories can be defined. Fields dest and gw
contain the cache serial number, the Modbus function number, and the upper and
lower edge of the memory block. Example:
>>
ART No 1:
items: 2
default gw: 00000000 (0.0.0.0 )
dest: gw:
00000003 00150010 (0.0.0.3 0.21.0.16 )
00010004 00250020 (0.1.0.4 0.37.0.32 )
>>
cache number 0000 for function 0003 from address 0010 to address 0015,
cache number 0001 for function 0004 from address 0020 to address 0025.
The Radiomaster sends regular reports for RS at Net timeout "SPe0tCt" intervals.
Besides this it also sends up-to-date messages about changes. The Radioslave
monitors if each RM has called at least once every so often "SPe0tCr". If not this
RM is disabled from the Master polling cycle until the RM calls again (after the
removal of defects).
Cache in RS is structured according to Modbus addresses. If addresses do not start
from one it is possible to leave the unused area of memory for the Slave (0 to N-1)
by using offset addresses, parameter "SPe0tCf". The number of blocks of cache can
then be adapted to the overall number of Slaves in the network with parameter
"SPe0tCu".
RS identifies individual Slave PLCs for their insertion into cache according to
MORSE addresses from which a message came. If it is necessary to distinguish a PLC
according to Modbus addresses it is possible to set it up by the type of address in
parameter "SPe0tCy".
The Modbus monitor function is useful for debugging. It is accessible from menu
"mp0M" and supplies information about cache in RS or RM.
Modbus monitor:
St(a)tion cache (d)ump
(q)uit
>>
By selecting "a" we obtain a dump of defined cache. In the example 10 blocks are
reserved, of which only address 05 is active. It is valid for further 37 s.
>>
Station activity in Modbus cache:
/1 /2 /3 /4 /5 /6 /7 /8 /9 /A /B /C /D /E /F /10
0 0 0 0 0 37 0 0 0 0 0
>>
By selecting "d5" we obtain a dump of cache 05 (length of cache according to the
definition in the Art table):
>>
cache data at position 5:
/0 /1 /2 /3 /4 /5 /6 /7 /8 /9 /A /B /C /D /E /F ASCII:
00000000 10 0A 09 06 69 11 22 FF BB BB ....i."...
3.4 TIME SYNCHRONISATION
Synchronisation between MORSE network modems is controlled from the "Ue" menu and
it can be linked to by time transfer through the Modbus protocol. Synchronisation
can be set between the Master PLC and RS or RM and Slave PLC. This only applies for
the first Slave, which is connected to RM by parameter "SPe0tM0". Time information
can be transferred in the direction Master -> RS, RM -> Slave or the opposite way.
Time with the set period is written to a selected address in RS or in the Slave PLC
or it is read from it.
Format of time data:
| gmtsec/32 | R/1 | ts/1 | R/4 | msec/10 | sec/8 | min/8 | hour/8 | day/8 |
| month/8 | year/8 |
gmtsec - current time, GMT indicated in seconds from 1.1.1970 is used (Unix time)
msec - milliseconds in the current second.
ts - timesavings, switch for summer/winter time (1 -summer, 0 -winter time)
Next items are generated from above mentioned.
It contain local time including correction of the time zone.
sec - current second
min - minutes
hour - hours (0 - 23)
mday - day of the month (1 - 31)
mon - month (0 - 11)
year - year (data in the year form - 1900)
R - reserved
3.5 WATCHDOG FUNCTION
The Slave PLC does not have the possibility of finding out whether communication
with the Radiomaster was interrupted. That is why there is the possibility here of
setting up the Watchdog function in the Radiomaster, which writes a designated word
to a selected address in the Slave PLC at regular intervals. Everything is set up
in the "SPe0ts" menu. The PLC can then regularly read and delete this record and
thus maintain information about the existence of the connection.
3.6. PACKET TYPE
Brief description of the packet type for the user interface:
|U/1|B/1|R/1|subt/5|
U - link security bit (1 - secured packet)
B - broadcast (multicast) bit (1 - broadcast packet)
R - reserved
subt - subtype
subt=0x09 - USER DATA
The basic type of packet for transporting data from the source to the
destination. By setting the bit U=1 we obtain the mostly used packet type 0x89, it
is secured user packet.
subt=0x0A - PROT DATA
This type of data is designed for data flow control in the user protocol. The
service of both preceding types of packets in the MORSE network is equivalent.
Packets are sent to the destination with the path and priority settings at the
participants addresses. An error message is sent to the original sender if a packet
is lost, but the packet carrying this error message can be, of course, lost as
well, and in this case silently.
subt=0x0Ch PACK ERROR REPORT
MORSE error message. First word is the Error Number, the rest of the message
holds more detailed information about the network error. Generation of these errors
can be turned off and on for whole network.
Some of these Error Numbers are here:
1 - PACKET_NOT_CONFIRMED
2 - STORE_TIMEOUT
3 - NO_CHANNEL_ASSIGNED
4 - ACCESS_TIMEOUT_ERROR
6 - WRONG_PACKET_FORMAT
7 - DEST_PROT_MISSING
8 - WRONG_PATH
9 - WIRE_LINK_FAIL
subt=0x10 - SERVICE REQUEST
Request for a MORSE service.
subt=0x12 - SERVICE REPORT
Response from the MORSE service.
3.7 EXAMPLES
Examples for transparent, packet and cache mode are given in the separate articles
"MODBUS examples".
Examples of packet mode are also contained in the older description "MODBUS 574".
4. CONFIGURATION PARAMETERS
MODBUS parameters:
(m)ode:RADIOMASTER (a)utomaster:OFF
(c)ache:ON (p)acket:OFF (t)rans:OFF
(M)aster (S)lave
(A)utomaster
(C)ache
(P)acket
(T)rans
(s)ervices (O)ld menu (sw ver =< 5.74)
(q)uit
>>
(m)ode:RADIOMASTER/RADIOSLAVE - modem position in the network
(a)utomaster:OFF - Radioslave can have the automaster function on,
it then assumes the Master function
when interrupting communication on RS458
(c)ache:ON (p)acket:OFF (t)rans:OFF - mode selection
Other parameters are divided into the submenus:
Parameters for Radiomaster:
>>(M)aster
master parameters:
(f)irst:691122FFh (s)econd:00000000h destination
d(e)vice type:PLC
Modbus slave addr: (0):5h (1):0h (2):0h (3):0h
(a)ddress mask:FFh
(p)eriod:10*10 ms
(t)imeout:20*100 ms
(q)uit
>>
(f)irst:691122FFh - address of Radioslave in the MORSE network,
00000000 = messages are sent back
(s)econd:00000000h - if this address is nonzero, then the copy of spontaneous
messages are sent to it, except messages caused "SPe0tCt"
d(e)vice type:PLC - choice between connected SEP technological unit and
normal PLC
Modbus slave addr: (0):5h (1):0h (2):0h (3):0h
- list of Slave stations included in the polling cycle
(a)ddress mask:FFh - masked part of the MORSE address is used as a Modbus
address
(p)eriod:100ms - period for polling Slave stations
(t)imeout:2000ms - max. time for waiting for a reply
Parameters for Radioslave:
>>(S)lave
slave parameters:
Modbus (a)ddress:FFh
(r)epeat discard:0
d(e)vice type:PLC
(q)uit
>>
Modbus (a)ddress:FFh - address of Slave stations in the Modbus network,
01 to FF
(r)epeat discard:0 - number of repeats from Master PLC, which are discarded
before one is sent to the radio network. Useful for the
Master PLC, which is not able wait for response.
d(e)vice type:PLC - choice between connected SEP technological unit and
normal PLC
Parameters for Automaster:
>>(A)utomaster
Modbus automaster:
t(i)meout:0s
master mode after switching:
(c)ache:ON (p)acket:OFF (t)rans:OFF
(q)uit
>>
t(i)meout:0s - after this idle period on the RS485 the Radiomaster with the
(a)utomaster parameter switched on takes the Radioslave task and continues
in the mode determined by the following three parameters
(c)ache:ON (p)acket:OFF (t)rans:OFF.
Upon restoring the activity of the original Radioslave the Radiomaster
returns to its task.
Parameters for Cache mode:
>>(C)ache
cache parameters:
(c)ache table No:1
# ART dest: gw:
# nnnnffff hhhhllll
# No Fce high low addr
# BEWARE! IF YOU CHANGE CONTENT OF THE TABLE,
# YOU SHOULD RESTART (INIT) THIS PROTOCOL!
radioslave only:
net (r)x TO - Mirror:30s
adr o(f)fset:0 n(u)mber:0 net addresses
address. t(y)pe: MORSE
(s)imulator:OFF
radiomaster only:
net (t)x TO - mirror:30s
(e)rr. report:NONE err. (a)dr:0h err. (m)ask:0000h
(o)ld cache menu (since sw.630)
(q)uit
>>
(c)ache table No:1 - Number of Art table, which specifies the cache memory
space.
radioslave only:
net (r)x TO - Mirror:70s - This timeout is the time over which RS waits for
a message from RM. If it does not arrive the Master PLC
disables it from the polling cycle.
adr o(f)fset:0 - Address shift in cache
(when Slave addresses does not start from 1).
n(u)mber:0 - Max. number ofSlave PLC.
address. t(y)pe: MORSE - Defines, if the position in cache is determined
according to MORSE or Modbus Slave address.
(s)imulator:OFF - For service purposes.
radiomaster only:
net (t)x TO - mirror:30s - The report period to RS for this case, then no cache
changings occured.
(e)rr. report: - the message for RS when the communication on RS458 halts
NONE - no message, reports with period "SPe0tCt" continue
SILENT - no extra message, reports with period "SPe0tCt" stop
DATMOLUX - particular customer mode
MASK - Upon losing communication over RS485 the current message is
sent to the Master but modified in such a way that set bits (m)
are added to a selected word (a) of the message by the OR
operation.
err. (a)dr:0h -address of choosen word from beginning of cash memory block
err. (m)ask:0000h - This word is added (by the OR operation) to the selected memory
word.
Parameters for packet mode:
>>(P)acket
packet parameters:
(A)RT table No.:0
(N)2H buffer:2000 (H)2N buffer:1000
Warning: Both addresses should be nonzero.
(q)uit
>>
(A)RT table No.:4 - selection of Art table for the translation of MORSE addresses
to Modbus addresses
(N)2H buffer:2000 - Net to Host, which is MORSE Net to Modbus
(H)2N buffer:1000 - Host to Net, which is Modbus to MORSE Net
- addresses in memory, at which the respective buffer for storing
data sent by the Modbus in packet mode starts. These addresses must be selected
identically at all participants of the Modbus network.
Here the term Net represents the connecting MORSE network (Radiomaster), the Host
is the connected PLC Slave.
Parameters for transparent mode:
>>T
transparent parameters:
CRC (a)uto:OFF
check (f)unction:ON
check a(d)dress:ON
check (C)RC:ON
(q)uit
>>
CRC (a)uto:OFF - for tests only, RM joins CRC to the packet received from RS
check (f)unction:ON - the check, if the function number is one of Modbus functions
check a(d)dress:ON - for RM, check if the address is contained in "SPe0tM0.1,2.3"
check (C)RC:ON - check CRC in the Modbus packet
Parameters for service mode:
>>(s)ervices
Modbus services:
(t)ime sync:ON (m)ode:SENDER (p)eriod:10s
time (a)ddr:3000h time sync (b)it:0000h
(d)ebug addr:69000011h
radiomaster only:
(w)dog bit:0000h wd(o)g addr:0000h wdog p(e)riod:0s
(q)uit
>>
(t)ime sync:ON - switches ON the function of transfer of time data between
the Master and the Slave defined in "slave addresses (0)"
(m)ode:SENDER - Radiomaster or Radioslave can be selected as SENDER (transmits
time), and the other as RECEIVER (receives)
(p)eriod:10s - period for transferring time data is only defined in
Radiomaster
time (a)ddress :3000h - address for saving time, Master and Slave
time sync (b)it:0000h - customer's function
(d)ebug address:69000011h - address for tuning purposes; all user packets, which
came to the CU are sent to this address, to which, for example, Setr or async.
link are connected. The entering of any nonzero value changes the behave of CU
from DTE to DCE (then in the Packet mode writes in (N)2H buffer).
(w)dog bit:0000h - word periodically written to "slave addresses (0)"
wd(o)g address:0000h - address of write to Holding Registers in Slave (0)
wdog p(e)riod:0s - write period
Parameters for watchdog are only set in Radiomaster and furnishes for PLC
Slave the possibility to check, if the connection with Radiomaster endures.
5. HISTORY
This description is valid from version sw 657.
Cache menu for version to sw 630 is contained in "SPe0tCo".
The menu for versions to sw 574 is in "SPe0tO".
The description for sw 574 (20.5.2002) including more detailed explanation and the
packet mode examples is in the article "MODBUS 574".