Rockwell-automation 1770-KF2 Data Highway or Highway Plus Interface Mo Instrukcja Użytkownika Pobierz pdf (Strona 132)

Message Packet Formats

Chapter 5

5-53

Data Type Size

If Bit 3 is a zero (0), the data type defined in the ID Value Field uses 7 or

less bytes for each piece of data. The actual number of bytes the data type

uses for each piece of data is then contained in the Size Value Field (Bits

0, 1, 2).

If Bit 3 is a one (1), the data type defined in the ID Value Field uses more

than 7 bytes for each piece of data. The Size Value Field (Bits 0, 1, 2)

contains the number of bytes which identify the number of bytes the data

type uses for each piece of data. These bytes follow the parameter byte

and any ID type bytes.

Examples

The order of the bytes is least significant to most significant. One or more

most significant bytes containing all zeros are permitted, but the fields

thus generated are not different from those that omit these bytes. Thus the

following descriptors each have an ID type of 4 (integer) and a size value

of 3 bytes:

Bit 76543210

01000011

Bit 76543210

01001001

Bit 76543210

01001010

00000011 00000011

00000000

Type/Data

Parameter

The following example shows type “I” (integer) type/data parameters:

Bit 76543210

01000001

11111110

ID = 3 (Integer)

Size = 1 Byte

Value = –2

Bit 76543210

01000010

11111110

00000000

ID = 3 (Integer)

Size = 2 Bytes

(MS)

(LS) Value = 254

1 2 ... 127 128 129 130 131 132 133 134 135 136 137 ... 234 235

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