Appendix D - Recovery after Timeout Flow
Simplify will attempt to transmit a message a parameterized number of times before assuming communications is lost.
Message flow is bi-directional. The POS device or Simplify can initiate a message. In order to avoid timeouts and retransmissions between the POS device and Simplify, each endpoint (POS device or Simplify) should read an incoming message, calculate the LRC (se Appendix E - LRC Calculation), and immediately respond with an ACK or NAK.
* Recommended configuration for timeout on ACK is at least 3 seconds.
Exception to Timeout/Recovery Rules
After a timeout on a non-critical message, Simplify does not expect an ACK and will not retry the message. Sending an ACK for a non-critical message will not cause any issue. The following messages are considered non-critical, with the exceptions noted:
(Tran Type 36-51)
|Status Identifier = 001|
(For information on Status Identifiers, see Field 0011 (User Data).)
The message flow without an ACK is shown below. If a Status Message is configured for no ACK, Simplify is ready for the next message after sending the Status message.