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
        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. 


Overview of Modbus commands for reading and writing from various parts of the PLC 
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


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

(s)ervices    (O)ld menu (sw ver =< 5.74)


slave parameters:
Modbus (a)ddress:FFh
(r)epeat discard:0
d(e)vice type:PLC

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.


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

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.


transparent parameters:
CRC (a)uto:OFF
check (f)unction:ON
check a(d)dress:ON
check (C)RC:ON

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.


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 

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:

| H2Ndesc/16 | H2Nfr/modbusMRU |

| 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 

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".


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 (        )
dest:    gw:
00000003 00150010 (      )
00010004 00250020 (      )
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 

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
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."...


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


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.


Brief description of the packet type for the user interface:


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. 

  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:

  Request for a MORSE service. 

subt=0x12 - SERVICE REPORT 
  Response from the MORSE service. 


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".


MODBUS parameters:
(m)ode:RADIOMASTER  (a)utomaster:OFF
(c)ache:ON  (p)acket:OFF  (t)rans:OFF

(M)aster (S)lave

(s)ervices    (O)ld menu (sw ver =< 5.74)

(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:

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

(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 
(p)eriod:100ms     - period for polling Slave stations  
(t)imeout:2000ms   - max. time for waiting for a reply

Parameters for Radioslave:

slave parameters:
Modbus (a)ddress:FFh
(r)epeat discard:0
d(e)vice type:PLC

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:

Modbus automaster:
master mode after switching:
(c)ache:ON  (p)acket:OFF  (t)rans:OFF

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:

  cache parameters:
(c)ache table No:1
# ART dest:       gw:
#     nnnnffff    hhhhllll
#     No  Fce     high low addr

  radioslave only:
net (r)x TO - Mirror:30s
adr o(f)fset:0  n(u)mber:0  net addresses
address. t(y)pe: MORSE

    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)

(c)ache table No:1       - Number of Art table, which specifies the cache memory
      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
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

Parameters for packet mode:

packet parameters:
(A)RT table No.:0
(N)2H buffer:2000  (H)2N buffer:1000
Warning: Both addresses should be nonzero.

(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:

transparent parameters:
CRC (a)uto:OFF
check (f)unction:ON
check a(d)dress:ON
check (C)RC:ON
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:

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

(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
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.


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". 

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