Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 123)

7–36 Communication Commands
Publication 1770Ć6.5.16 - October 1996
The type/data parameter is a variable length field. The most
significant bit of each nibble determines additional bytes used. The
value of this field can be extended to a 7-byte unsigned integer. The
bytes are ordered least to most significant. All zero most-significant
bytes are permitted, but the fields generated by them are no different
than those that omit these insignificant bytes. The following three
descriptors are all permitted and equivalent:
Important: Your software must be able to handle all three cases.
Case 1 Case 2 Case 3
0100 0011 0100 1001 0100 1010 0100 0011 0100 1001 0100 1010
0100 0011 0000 0011
0000 0011
0100 0011 0000 0011
0000 0000
These all have an ID value of 4 and a size value of 3.
Example 1: Type/data parameter for writing or reading integer data
This example shows the type/data parameter for writing or reading integer (ID = 4)
data, with each element of data 2 bytes long.
0 1
type ID
data size contained
flag byte 0 1 0 0 0 0
data size
type ID contained
in bits 6, 5, 4 in bits 2, 1, 0
PLCĆ5 Type/Data
Parameter Examples