Omron NT31 Series, Operation Manuals

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Outline of Communications Section 9-3
S Processing differences according to command length
- If a command is too long because it has been incorrectly specified, an error
response for a command length error is returned.
- If a command is short because it has been incorrectly specified, a communica-
tion error (time out) occurs.
S Command transmission intervals
- If commands are sent too frequently, processing at the NT31/NT31C will not
be able to keep pace with them and a communication error (buffer overflow)
will occur.
- Use the flow control to prevent a buffer overflow.
S
Order of priority of input communication commands
- When a reason for input notification arises during processing of a command
from the host, the input command is issued only after the ongoing command
processing has been completed.
S Check sum
- The checksum of the command response is the 2 digits ASCII code which is
indicated using lower one--byte of the total sum (in unit of bytes) of the follow-
ing, from the [ESC] code at the beginning to the character immediately before
the checksum value. It can be omitted by specifying the parameter used to
omit sum value.
If “ON” is set for the “Comm. Auto-return” memory switch, communication er-
rors are not displayed on the screen even if they occurs. However, in case of
time out error at the NT31/NT31C side, an error message is displayed on the
screen and the operation is stopped.
Reference: Whether or not the error response is returned depends on the memory switch set-
ting made for “Comm. Auto-return” and error type.
For details, refer to “Error Response” in page 598.