5
edoCemaNnoitinifeD
10noitcnuFlagellI tonsideviecernoitcnufegassemehT
noitcaelbawollana
20 ataDlagellI
sserddA
dleifatadehtniecnerefersserddaehT
sserddaelbawollanatonsi
30eulaVataDlagellI sidleifatadehtnidecnerefereulavehT
evalsdesserddaehtnielbawollaton
70 evitageN
tnemgdelwonkcA rorreegassemdevieceR
80 ytiraPyromeM
rorrE
enonirorrenasetacidnikcehcytiraP
deviecersretcarahcehtfoeromro
Table 4.1 Modbus Exception Responses
4 MODBUS PROTOCOL
golanA
tupnI
lioCsubdoM
.ylnOdaeR
,KOtupnI=0
deliaftupnI=1
golanA
tupnI
lioCsubdoM
.ylnOdaeR
,KOtupnI=0
deliaftupnI=1
1A10001D9100
2A20002D0200
3A30003D1200
4A40004D2200
5A50005D3200
6A60006D4200
1B70001E5200
2B80002E6200
3B90003E7200
4B01004E8200
5B11005E9200
6B21006E0300
1C31001F1300
2C41002F2300
3C51003F3300
4C61004F4300
5C71005F5300
6C81006F6300
Table 5.1 Analog Input Fail States
5 OPERATING MODE
4.1 Modbus Commands Supported
The following Modbus commands are supported:
01 Read Coil Status –reads the on/off status of up to 120
consecutive digital states, starting at a specified address.
The instrument returns zeros for points which do not contain
defined data
03 Read Holding Registers –reads up to 120 consecutive
anolog values, starting from a specified address. The
instrument returns zeros for registers which do not contain
defined data.
05 Force Single Coil –sets the value of a single coil (digital
signal) at the specified address. The data value must be
FF00Hex to set the signal ON and zero to turn it OFF. The
instrument returns an exception response if the register is
not currently writeable.
06 Preset Single Register –sets the value of a single register
(analog value) at the specified address. The instrument
returns an exception response if the register is not currently
writeable. Limits defined in configuration are applied to the
value before storage.
08 Loopback Diagnostic Test –used to test the integrity of
Modbus transmissions. The instrument returns the message
recieved.
15 Force Multiple Coils –the instrument carries out updates
that are valid and returns an exception response if any of the
coils are not currently writeable.
16 Preset Multiple Registers –the instrument carries out
updates that are valid and generates an exception response
if any of the registers are not currently writeable.
Information.
•Negative numbers are represented in '2's complement'
format, e.g 1000 = 03E8 (Hex), –1000 = FC18 (Hex)
•The instrument cannot accept a new message until the
current message has been processed and a reply sent to
the master (maximum response time 50ms).
•The instrument monitors the elapsed time between
receipt of characters from the host. If the elapsed time
between two characters is 3.5 character times, the slave
assumes the second character received is the start of a
new message.
5.1 Operating Mode Modbus Coils
Tables 5.1 to 5.11 detail the contents of each Modbus coil. Each
coil is assigned a register that can have one of two values: 0000
and 0001.
4.2 Modbus Exception Responses
If the instrument detects one of the errors listed in Table 4.1 while
receiving a message from the host system, it replies with a
response message consisting of the instrument's Modbus
address, the function code, the error code and error check
fields.
