UD78 User Guide
Issue code: 78nu2
A-3
Note
It is important to realize that when using group
addressing, the Drives will not acknowledge the command.
(If several Drives try to reply at the same time, they would
cause meaningless data to appear on the serial
communications bus.)
For security, the format of the transmitted address requires that each digit
of the two-digit address is repeated: the address of Drive number 23 is sent
as four characters, eg:
2 2 3 3
The serial address follows immediately after the first control character of
the message (
EOT
).
Parameter identification
For transmission of their values, all parameters are identified by four digits
representing the menu and the parameter number, but without the decimal
point.
Example
To send a message to menu 4, parameter 26, write
0426
(the leading zero
must be included)
To send a message to menu 16, parameter 3, write
1603
.
Data field
Data to be sent or requested occupies the characters immediately after the
parameter number. The minimum length of the data field within a message
structure is two characters.
The data is normally expressed as a decimal numeric value; the first
character of the data field (
D1
) can be only one of the following:
Space (32 dec.)
+
–
Block checksum (BCC)
In order to protect the system against messages that have become
corrupted in transmission, all write messages and data responses are
terminated by the block checksum character (
BCC
). See
Calculating the
block checksum (
BCC
)
later in this appendix.