Mitsubishi Electric QJ71MB91 User Manual page 41

3
SPECIFICATIONS
(2) RS-422/485 interface operation
(a) RS-422/485 interface configuration
Figure 3.4 RS-422/485 interface configuration
(b) RS-422/485 interface operation
(c) QJ71MB91 transmission start timing, transmission process complete timing
For RS-422/485 interface, the configuration of driver (send)/receiver (receive)
component of the QJ71MB91 is as shown in the following diagram.
Driver
SDR
Send data
SDB
1
Output Control Input (* )
RDA
Receiver
Receive data
RDB
* 1 The "output control input" (also referred to as send gate) of the driver (send) component
determines whether to output data externally from SDA, SDB.
When the "output control input" in the above figure is ON, the impedance status is
low (data transmittable).
In addition, when the "output control input" is OFF, the impedance status is high
(data not transmitted).
• Transmission start timing
After releasing the high impedance status indicated in above (a) and (b), and
outputting two or more character data during data transmission, output the
actual data.
• Transmission process complete timing
Data transmission time for data of 1 bit or less is required as the H/W gate
OFF time to complete the transmission process (high impedance status) after
finishing data transmission.
(Transmission speed set in the QJ71MB91 is targeted.)
(Output control input)
Target device side
QJ71MB91 side
(Output control input)
Figure 3.5 Transmission process complete timing
3.3.3 Precautions when transferring data using RS-422/485 line
Data
Outputs a mark with
2 characters or more
Data transmission
time range
H/W gate OFF time
(Refer to explanation above)
OFF time range of
ON time range of output
output control input
control input
(High impedance status)
(Low impedance status)
QJ71MB91 can send data. QJ71MB91 can receive data.
3.3 RS-422/485 Interface Specification
1
2
3
4
5
6
Data
7
8
3
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