Microscan MS-4 User Manual page 352

Communications Protocol
Error Condition 2
HOST_TX
IMAGER_TX
HOST_TX
timeout reached...
IMAGER_TX
HOST_TX
(Retry Event)
IMAGER_TX
HOST_TX
IMAGER_TX
Error Condition 3
HOST_TX
IMAGER_TX
HOST_TX
(Retry Event)
IMAGER_TX
HOST_TX
IMAGER_TX
The protocol makes 3 retry attempts before data is flushed and transfer is aborted.
A-20
'RES' '0x1C' 'REQ' (Poll Unit 1 for data)
'0x1C' 'STX' <T/00000> 'ETX' 'LRC'
'Nothing' (Host should 'ACK' here)
'REQ' (Unit requests an 'ACK' again)
'NAK' (Host rejects data frame)
'0x1C' 'STX' <T/00000> 'ETX' 'LRC' (Unit sends again)
'ACK' (Host receives data)
'RES' (Terminate Transfer 1)
'RES' '0x1C' 'REQ' (Poll Unit 1 for data)
'0x1C' 'STX' <T/00000> 'ETX' 'BAD LRC'
'NAK' (Host rejects bad LRC data)
'0x1C' 'STX' <T/00000> 'ETX' 'GOOD LRC' (Unit sends again)
'ACK' (Host receives data)
'RES' Terminate Transfer 1)
MS-4 Imager User's Manual