Appendix C - Example Link Level Exchanges (Serial Communications and USB emulating Serial)

The POS device will attempt to transmit the message a parameterized number of times before assuming communications are lost.

Normally the POS and Simplify respond to each message received with an ACK. If a corrupted message is received, the response is a NAK.

normal message flow with all ACKsmessage flow with ACKs and one NAK