Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual de usuario descargar pdf (Pagina 125)

7–38 Communication Commands

Publication

17706.5.16 - October 1996

Important: There are also some limitations on the basic commands

SLC 500 family nodes support:

Command Limitation

Diagnostic Loop Maximum data field size is 95 bytes, not 243.

Unprotected Read

Maximum data field size is 95 bytes, not 244. In addition, the

Addr field is used as a word address instead of a byte address,

and the Size field may contain either an even or odd value.

Unprotected Write

Maximum data field size is 94 bytes, not 244. In addition, the

Addr field is used as a word address instead of a byte address.

When using SLC terminology:

• The address field in the unprotected read and unprotected write

commands is used as the word offset into the file

• Thus, to read N9:9 from an SLC 500, put 9 in the address field

(after converting it to 09 hex)

Important: The address fields of unprotected reads and unprotected

writes are used as word addresses instead of the byte

addresses used in the PLC-2, 1774-PLC, and PLC-5

processor. Because of this, existing software drivers

that communicate with the these processors do not work

with SLC 500 family processors, unless you set bit

S:2/8 to a logical one. The SLC 500 processor then

changes to byte addressing mode. This bit is reset to

logical zero by default.

SLC 500 Information

Reading and Writing

SLC 500 Data

Reading and Writing

SLC 500 Data

(using PLC2 terminology)

1 2 ... 120 121 122 123 124 125 126 127 128 129 130 ... 250 251

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Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Manual de usuario Pagina 125