Ametek 7230 HT Digital Probe Manual de usuario descargar pdf (Pagina 13)

2.13 - Byte Ordering

In the Modbus slave conﬁ guration, data can be ac-

cessed as integers (16 bits), long integers (32 bits),

and ﬂ oating point value (32 bits). The order that the

bytes are sent must be known by the master in order to

assembly the bytes into the correct value. Byte order-

ing can have a few different terminologies.

1) Big/Little Endian.

2) Byte order by number, with 1 indicating the most

signiﬁ cant part of the value, and 4 the least signiﬁ -

cant.

3) Word/Byte, indicating which word (16 bits, high or

low) is sent ﬁ rst, and which byte of the word (high or

low) come ﬁ rst in that byte.

See the following example for accessing a product

reading of 46.60 inches. The integer value will be

4660, which translates to the hex number 0x00001234.

The individual bytes, 0x00, 0x00, 0x12, and 0x34 can

be sent the following 4 ways for 32 bits values:

1) Big Endian, Byte order 1234, High Word High Byte

(HWHB) Order sent: 0x00, 0x00, 0x12, 0x34

2) Little Endian, Byte order 4321, Low Word Low Byte

(LWLB) Order sent: 0x34, 0x12, 0x00, 0x00

3) Big Endian Byte Swapped, Byte order 2143, High

Word Low Byte (HWLB) Order sent: 0x00, 0x00,

0x34, 0x12

4) Little Endian Byte Swapped, Byte order 3412, Low

Word High Byte (LWHB)

Order sent: 0x12, 0x34, 0x00, 0x00

The individual bytes 0x12, and 0x34 can be sent the

following 2 ways for 16 bits values:

1) Big Endian, Byte order 12, High Byte ﬁ rst (HB)

Order sent: 0x12, 0x34

2) Little Endian, Byte order 21, Low Byte ﬁ rst (LB)

Order sent: 0x34, 0x12

2.14 - Modbus Map

Use the following tables to ﬁ nd the register number

for the desired format. First, go to the section for the

number format you desire (integer, long integer, or

ﬂ oating point). Then ﬁ nd the table with the desired

units, English or metric. Then ﬁ nd the value (product,

interface, average temperature, etc) in the left hand

column. Next, ﬁ nd the desired byte ordering across the

top row. The corresponding entry at the intersection of

these 2 items gives the register that should be speciﬁ ed

in the Modbus master request message. The number

of registers needed to obtain the value is also speciﬁ ed

for each format.

NOTE:

HWHB = High Word High byte

LWHB = Low Word High Byte,

HWLB = High word low byte

LWLB = Low Word low byte

2.15 Modbus Registers

Integer (16 bit Signed) formats

Signed 16 bit Integer, 16 bits of data per register,

1 register needed to get value English Units,

inches and degrees F

Data Big Endian,/

Hi Byte ﬁ rst

Little Endian/

Low Byte ﬁ rst

Product 31803 32003

Interface 31805 32005

product temperature 31807 32007

interface temperature 31809 32009

average temperature 31811 32011

status 31813 32013

Span 31815 32015

temperature 1 31817 32017

temperature 2 31819 32019

temperature 3 31821 32021

temperature 4 31823 32023

temperature 5 31825 32025

max temperature 31827 32027

temperature sensor 1 location

(closest to bottom)

31829 32029

temperature sensor 2 location 31831 32031

temperature sensor 3 31833 32033

temperature sensor 4 location 31835 32035

temperature sensor 5 location

(closest to top)

31837 32037

Software version 31899 32099

Data Big Endian,/

Hi Byte ﬁ rst

Little Endian/

Low Byte ﬁ rst

Product 31903 32103

Interface 31905 32105

product temperature 31907 32107

interface temperature 31909 32109

average temperature 31911 32111

status 31913 32113

Span 31915 32115

temperature 1 31917 32117

temperature 2 31919 32119

temperature 3 31921 32121

temperature 4 31923 32123

temperature 5 31925 32125

max temperature 31927 32127

temperature sensor 1 location

(closest to bottom)

31929 32129

temperature sensor 2 location 31931 32131

temperature sensor 3 31933 32133

temperature sensor 4 location 31935 32135

temperature sensor 5 location

(closest to top)

31937 32137

Software version 31999 32199

Signed 16 bit Integer, 16 bits of data per register, 1

centimeters and degrees C

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 24 25

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