YOKOGAWA F3RS22-0N, User Manual

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4-14
IM 34M6H21-01E 2nd Edition : Aug, 2001-00
„
X
ON
/X
OFF
Control
This feature prevents overflow in the communication buffer through the exchange of
special characters. This feature only applies in full duplex communications.
Table 4.8 X
ON
/X
OFF
Operation
Classification Operation
Receiving end When the space in the input buffer falls below one quarter, transmit X
OFF
.
When the space in the input buffer rises above half, transmit X
ON.
When data is received in the X
OFF
state after X
OFF
transmission, the X
OFF
character is retransmitted. The character-to-character timer is inactive in
the X
OFF
state and becomes active once X
ON
is received.
Transmitting
end After the specified X
OFF
character is received, sending is stopped within 2
characters.
The received X
OFF
character is not passed as receive text to BASIC.
The system will switch to the X
ON
state when power is switched on or when the module,
port or buffer is reset. Any single character can be set as the X
ON
/X
OFF
character.
(default is DC1/DC3).
(Example) When using X
ON
/X
OFF
control for both sending and receiving characters
10 ASSIGN RS22=5
20 CONTROL 5,2,25;3 :!Specify XON/XOFF control.
30 RESET 5,2,1 :!Reset buffer
However, X
ON
/X
OFF
control is only available in character communications. The X
ON
/X
OFF
characters are not sent during text transmission.
„
Break Signal
The break signal is a special signal that sends data containing a type of framing error
(all bits are “1”). This communication module handles break signal on both sending and
receiving.
z
Sending a break
(example) Send the break signal after a 300 ms interval
1000 CONTROL 5,2,20;300 :!Specify send time for break signal
1010 CONTROL 5,2,101;1 :!Specify to send a break
z
Receiving a break
Receiving a break signal causes an error (82-D4: receive error).
However, it can also be identified using an interrupt input. For details, see Section 4.3