Rockwell Automation 2706-F11J_F11JC_F21J_F21JC DL50 INSTALLATION MANUAL - Manual (Page 52)

Chapter 5
Serial Communications
5–2
The simplex data packet consists of 6 data fields as shown below:
Optional Control
Byte
Field 1
1 Byte
ASCII Text or
Special Control
Characters
Field 2
0-250 Bytes
Optional
Display Mode
Field 3
1 Byte
Slave Address
Field 4
1 Byte
Line Number
Field 5
1 Byte
Carriage Return
Field 6
1 Byte
Note: Simplex protocol is compatible with Allen-Bradley DL20 and DL40
message displays.
Field 1: Optional Control Byte
This is an optional field which indicates whether the text is to be buffered or
displayed when it is received. The following control characters are used:
Table 5.B
Control Byte Characters (Simplex)
Control Character
Decimal
Value
Function
Ctrl-A 1 Append the characters to buffer.
Ctrl-B 2 Append characters to buffer then display.
Ctrl-C 3 Clear display line(s).
Ctrl-L 12 Initialize DL50 for Bootstrap.
The ability to append characters to the display buffer (Ctrl-A) and to display
the buffer contents (Ctrl-B) allows long message text to be sent using
multiple data packets.
The command for initializing the Bootstrap Mode (Ctrl-L) is described in
Chapter 7.
If this control byte is not included in the message packet, the DL50 will
default to displaying the text. All other values of the control character are
ignored.
Field 2: ASCII Text
This field contains the ASCII characters and/or special ASCII control
characters (up to 250) that are to be displayed by, or to control, the DL50.
If the Optional Display Mode byte is not sent, and the packet contains more
text than can be displayed on one line of the display, the message will be
truncated (unless message line number is 30, see Table 3.A).
Simplex Protocol