Panasonic FP2 Series, Руководство пользователя

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Flow Control
FP2 Serial Data Unit
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Flow Control
In serial communication, if the receiving side cannot keep up with the data being sent,
the received buffer overflows, and subsequent data is discarded. In order to avoid this
kind of situation, a type of control called flow control is used, in which data transmission
can be temporarily stopped and then restarted.
With the serial data unit, signal lines such as RS (Request to send) and ER (Data
terminal ready), CS (Clear to send) and CD (Received line signal detector) are available
for flow control. These are separate from the SD (Sent Data) and RD (Received Data)
signal lines, and are used in hardware flow control.
When the serial data unit is connected to the external device with an RS232C, the wiring
is connected differently, depending on whether or not flow control is used. The
differences are explained here using two typical examples of wiring, shown below.
3 − line connection (no RS or ER control) with no flow control
These are connected with the SD (Sent Data) and RD (Received Data) of the two
devices crossed. This is the basic method used to connect the serial data unit to the
external device.
1
Pin No. Abbrev. Pin No. Symbol
FP2 serial data unit side (9 pins)
RS232C device side
2
3
4
5
6
7
8
9
FG
SD
RD
RS
CS
SG
CD
ER
1
2
3
4
5
6
7
8
20
FG
SD
RD
RS
CS
SG
CD
ER
Protective ground
Sent data
Received data
Request to send
Clear to send
Signal ground
Received line signal detector
Data terminal ready
Signal name
Shielding wire
DR
Not used
Notes
•
When the serial data unit is being used with no control
signals, it is not necessary to connect the RS and CS signals,
or the CD and ER signals, but we recommend making the RS
— CS and CD — ER signal connections as shown above.
The RS — CS connection should also be made on the RS232C
device side.
•
When the power supply is turned on, the “Control Signals CS
and CD” setting in the transmission format settings is set to
“Invalid”.