443
Command and Response Formats
Section 6-4
When commands are issued to the host computer, the data is transmitted in
one direction from the PC to the host computer. If a response to a command is
required, use a Host Link communications command to write the response
from the host computer to the PC.
6-4
Command and Response Formats
This section explains the formats for the commands and responses that are
exchanged in Host Link communications.
6-4-1
Commands from the Host Computer
When a command is issued from the host computer, the command and
response formats are as shown below.
Command Format
When transmitting a command from the host computer, prepare the command
data in the format shown below.
@
An “@” symbol must be placed at the beginning.
Node No.
Identifies the PC communicating with the host computer.
Specify the Host Link node number set for the PC in the PC Setup (DM 6648
and DM 6653 for CPU Unit, DM 6553 and DM 6558 for Serial Communica-
tions Board).
Header Code
Set the 2-character command code.
Text
Set the command parameters.
FCS
Set a 2-character Frame Check Sequence code. See page 445.
Terminator
Set two characters, “
*
” and the carriage return (CHR$(13)) to indicate the end
of the command.
Response Format
The response from the PC is returned in the format shown below. Prepare a
program so that the response data can be interpreted and processed.
@, Node No., Header Code
Contents identical to those of the command are returned.
End Code
The completion status of the command (e.g., whether or not an error has
occurred) is returned.
Text
Text is returned only when there is data such as read data.
x 10
1
@
FCS
x 10
0
*
↵
Node No.
Header
code
Text
Terminator
@ x 10
1
x 10
0
x 16
1
x 16
0
FCS
*
↵
Node No.
Header
code
End code
Text
Terminator
