User’s Manual Series TAS-1
FEMA ELECTRÓNICA - Page 13
7.3.6- CHARACTER STRUCTURE
Bit structure for the characters on protoco-
los ModBus RTU and ModBus ASCII
7.3.7- MODBUS FRAME STRUCTURE-II
7.3.5- MODBUS FRAME STRUCTURE-I
T1 = Time between two characters
T2 = Time between end of question and start of response
T3 = Time between end of responde and start of next question
7.3.4- CONNECTIONS AND BUS TERMINATOR
RESPONSE : Communication SLAVE to MASTER
ADDRESS
1 CARACTER
Instrument Address
FUNCTION
1 CARACTER
Function 04H, register read
LENGTH
1 CARACTER
Number of data characters following
DATA
X CARACTERES
Response data*
CRC
2 CARACTERES
Control Checksum
QUESTION : Communicacion MASTER and SLAVE
ADDRESS
1 CHARACTER
Instrument Address
FUNCTION
1 CHARACTER
Function 04H, register read
READING START REGISTER
2 CHARACTERS
Register 00 00H = Display Value
NUMBER OF REGISTERS TO READ
X CHARACTERS
02 = 2 registers (4 bytes)
CRC
2 CHARACTERS
Control Checksum
START DATA
PARITYSTOP
TOTAL BITS
RTU
1
8
P
1
11
1
8
I
1
11
1
8
--
2
11
ASCII
1
7
P
1
10
1
7
I
1
10
1
7
--
2
10
T2 MAX
(RTU and ASCII)
38400 4.3 mSeg
19200 5.7 mSeg
9600
9.2 mSeg
4800
15.5 mSeg
2400
27 mSeg
T1 (min/max)
RTU
0CT / 3CT
ASCII
0CT / ---
T3 (min/max)
RTU
3.5CT / --
ASCII
--- / ---
Conections .- Cables A
and B as Standard
Modbus
Terminator .- Place jumper
if the BUS ends on this
instrument
Example for a Modbus-RTU frame .- Start Character corresponds with instrument address and final character
corresponds with the CRC Security Code
In Modbus-ASCII Start and End characters are specífic
Terminal 13 A
Terminal 14 B
