Error Condition 1

HOST_TX	`RES' `0x1C' `REQ' (Poll Unit 1 for data)
SCANNER_TX	`0x1C' `STX' <T/00000> `ETX'
HOST_TX	`Nothing' (Host should `ACK' here)
timeout reached...
SCANNER_TX	`REQ' (Unit requests an `ACK' again)
timeout reached...
SCANNER_TX	`REQ' (Unit requests an `ACK' again)
timeout reached...
SCANNER_TX	`REQ' (Unit requests an `ACK' again)
timeout reached...
SCANNER_TX	`RES' (Terminate Transfer 1, data is flushed)

Error Condition 2

HOST_TX	`RES' `0x1C' `REQ' (Poll Unit 1 for data)
SCANNER_TX	`0x1C' `STX' <T/00000> `ETX'
HOST_TX	`Nothing' (Host should `ACK' here)
timeout reached...
SCANNER_TX	`REQ' (Unit requests an `ACK' again)
HOST_TX	`NAK' (Host rejects data frame)
(Retry Event)
SCANNER_TX	`0x1C' `STX' <T/00000> `ETX' (Unit sends again)
HOST_TX	`ACK' (Host receives data)
SCANNER_TX	`RES' (Terminate Transfer 1)

The protocol makes 3 retry attempts before data is flushed and transfer is aborted.