
MDI-4000 Series Serial Interface Manual
23
BUSY/READY
The scan engine and the host system notify each other when they are ready to receive data
(BUSY/READY) through their RTS line. When they are connected (as shown in the next
diagram), the CTS line can be used to check if the other side is busy (off) or ready to receive
data (on).
Figure 14: BUSY/READY
The scan engine’s RTS line is normally on (ready to receive data) except when processing
received data, transmitting data, and processing 1D or 2D menu barcodes. When the scan
engine wants to send data, it makes sure that the host is ready to receive data by seeing if its
CTS line is on. If the CTS line is off, the scan engine does not send the data and waits for a
specific timeout period for the CTS line to be turned on. If the CTS line is not turned on within
the specified time, the data transmission is canceled.
Figure 15: RTS/CTS Data Transmission
4.1.6.2
CTS, TxD Signal Timing
When the CTS line is pulled low during a transmission, the transmission stops. When the CTS
line is pulled high again, the transmission continues.
Figure 16: CTS, TxD Signal Timing
TxD
CTS
RTS
Cannot Receive Command
Scan Engine
Host System
CTS
RTS
RxD
Decode
Finish
Wait to
Send
Send
Wait to
Send
Send
Software
Buzzer
CTS
TxD
n-1
n
n+1 n+2
Scan Engine
Host System
TxD
TxD
RxD
RxD
RTS
RTS
CTS
CTS
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