Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 116)

7–29 Communication Commands
Publication 1770Ć6.5.16 - October 1996
Data Type ID (Bits 4Ć7) Data Type Size (Bits 0Ć3)
The following table contains a list of the types of data you can
read and write and the ID value of each:
If the data type defined in
the ID Value field uses
Then enter
Data Type ID Type of Data 7 or fewer bytes for each
piece of data
zero (0) in bit 3 of the flag byte. Enter the
actual number of bytes used for each
element of data in bits 0, 1, and 2 (Size
Value Field).
1
2
3
4
5
6
7
8
9
15
16
bit
bit string
byte (or character) string
integer
AllenĆBradley timer
AllenĆBradley counter
AllenĆBradley general control structure
IEEE floating point
array of similar elements
address data
binaryĆcoded decimal (BCD)
more than 7 bytes for each
element of data
one (1) in bit 3 of the flag byte. In bits 0, 1,
and 2, you enter the number of bytes that
will contain the number of bytes used for
each element of data. These additional
size value bytes follow the flag byte and any
ID Type bytes.
For example, if each element of data used 8 bytes, then you set bit 3 to 1
(because the value 8 cannot fit into bits 0, 1, and 2). Bits two, one, and zero
would be set to 0, 0, 1 (respectively), to signify that the number of bytes per
element of data (8) will be contained in one byte that follows the flag byte
and any ID Type bytes.
If the Data
Type ID is
Then set bit 7 of the flag byte to
7 or less zero (0), and encode the ID value for the
data type in the bits 4, 5, and 6 (ID Value
Field).
greater than 7 one (1). In bits 4, 5, and 6, you insert the
number of bytes to follow that contain the
data type ID value (usually 1). These
additional ID value bytes follow directly after
the flag byte.
For example, if you were sending address data, then bit 7
would be set to 1 (because the address ID value 15 cannot fit
into bits 4, 5, and 6). Bits six, five, and four would be set to 0,
0, 1 (respectively), to signify that the data ID value (15) will be
contained in one byte that follows the flag byte.
For examples of type/data parameter, see page 7–36 .