Section 8. Operation
440
8.10.3.2.4 Supported Modbus Function Codes
Modbus protocol has many function codes. CR800 commands support the
following.
Supported Modbus Function Codes
Code
Name
Description
01
Read coil/port status
Reads the on/off status of discrete
output(s) in the ModBusSlave
02
Read input status
Reads the on/off status of discrete
input(s) in the ModBusSlave
03
Read holding registers
Reads the binary contents of holding
register(s) in the ModBusSlave
04
Read input registers
Reads the binary contents of input
register(s) in the ModBusSlave
05
Force single coil/port
Forces a single coil/port in the
ModBusSlave to either on or off
06
Write single register
Writes a value into a holding register in
the ModBusSlave
15
Force multiple coils/ports Forces multiple coils/ports in the
ModBusSlave to either on or off
16
Write multiple registers
Writes values into a series of holding
registers in the ModBusSlave
8.10.3.2.5 Reading Inverse Format Modbus Registers
Some Modbus devices require reverse byte order words (CDAB vs. ABCD).
This can be true for either floating point, or integer formats. Since a slave CR800
uses the ABCD format, either the master has to make an adjustment, which is
sometimes possible, or the CR800 needs to output reverse-byte order words. To
reverse the byte order in the CR800, use the
MoveBytes()
instruction as shown in
the sample code below.
for
i = 1
to
k
MoveBytes
(InverseFloat(i),2,Float(i),0,2)
MoveBytes
(InverseFloat(i),0,Float(i),2,2)
next
In the example above,
InverseFloat(i)
is the array holding the inverse-byte
ordered word (CDAB). Array
Float(i)
holds the obverse-byte ordered word
(ABCD).
See
Endianness
(p. 559).
Summary of Contents for CR800 Series
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Page 446: ...Section 8 Operation 446 8 11 2 Data Display FIGURE 100 CR1000KD Displaying Data ...
Page 448: ...Section 8 Operation 448 FIGURE 102 CR1000KD Real Time Custom ...
Page 449: ...Section 8 Operation 449 8 11 2 3 Final Storage Data FIGURE 103 CR1000KD Final Storage Data ...
Page 450: ...Section 8 Operation 450 8 11 3 Run Stop Program FIGURE 104 CR1000KD Run Stop Program ...
Page 452: ...Section 8 Operation 452 FIGURE 106 CR1000KD File Edit ...
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Page 523: ...Section 11 Glossary 523 FIGURE 116 Relationships of Accuracy Precision and Resolution ...
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