Setup 2

Address	0x01 (translates to) Poll Req @ `0x1C', Unit Select @ `0x1D'
RES	0x04
REQ	0x05
STX	0x02
ETX	0x03
ACK	0x06
NAK	0x15
LRC	enabled

Transfer 1

HOST_TX	`RES' `0x1D' `REQ' (Select Unit 1 to receive data)
SCANNER_TX	`0x1D' `ACK' (Unit responds with its address)
HOST_TX	`STX' <T> `ETX' `LRC'
SCANNER_TX	`0x1D' `ACK' (Unit responds with its address)
HOST_TX	`RES' (Terminate Transfer 2)

Transfer 2

HOST_TX	`RES' `0x1C' `REQ' (Poll Unit 1 for data)
SCANNER_TX	`0x1C' `STX' <T/00000> `ETX' `LRC'
SCANNER_TX	`ACK'
HOST_TX	`RES' (Terminate Transfer 1)

Starting with a `RES' ensures a clean transaction, without "leftovers" from the previous transaction.