Mindeo ES4200, Руководство пользователя

Страница: 84 / 108

78
and issues transmit error beep.
When ACK/NAK handshaking is disabled, the CMD_NAK message will not be sent.
It is not necessary to respond to a valid ACK or NAK message.
For example:
Length Opcode Status Cause Checksum
0x04 0x4E 0x00 0x40 (the parameter wishing to change is not existed) 0xFF 0x6E
Table 4-5 describes NAK types supported by the scanner.
Table 4-5 Scanner-supported NAK types
NAK Type Meaning Receiver Action
NAK_RESEND Checksum incorrect.
Ensure checksum is correct. Limit
number of resends. Send packet again
with resend bit set (with the retransmit
status bit set).
NAK_NO_PARA
the parameter wishing to
change is not existed
Do not send the same message again.
Developer should ensure the proper
message is sent.
NAK_OUT_OF_RANGE
the parameter wishing to
change exceeds the range
NAK_BAD_CONTEXT
Host does not recognize the
opcode.
NAK_DENIED
Host is unable to comply with
the requested command (e.g.,
scanning mode setting is out of
range).