Ssi Transactions; General Data Transactions; Transfer Of Decode Data - Motorola Symbol MS4404 Integration Manual

SSI Transactions

General Data Transactions

ACK/NAK Handshaking
If you enable ACK/NAK handshaking (the default), all packeted messages must have a CMD_ACK or CMD_NAK
response, unless the command description states otherwise. Keep this handshaking enabled to provide feedback
to the host. Raw decode data and WAKEUP do not use ACK/NAK handshaking since they are not packeted data.
Following is an example of a problem that can occur if you disable ACK/NAK handshaking:
•
The host sends a PARAM_SEND message to the decoder to change the baud rate from 9600 to 19200.
•
The decoder cannot interpret the message.
•
The decoder does not implement the changes the host requested.
•
The host assumes that the parameter changes occurred and acts accordingly.
•
Communication is lost because the change did not occur on both sides.
If you enable ACK/NAK handshaking:
•
The host sends a PARAM_SEND message.
•
The decoder cannot interpret the message.
•
The decoder CMD_NAKs the message.
•
The host resends the message.
•
The decoder receives the message successfully, responds with CMD_ACK, and implements parameter
changes.

Transfer of Decode Data

The Decode Data Packet Format parameter controls how decode data transmits to the host. Enable this parameter
to send data in a DECODE_DATA packet. Disable this parameter to transmit data as raw ASCII data.
NOTE When decode data transmits as raw ASCII data, ACK/NAK handshaking does not apply regardless of its
parameter setting.
SSI Interface 8 - 3