RKC INSTRUMENT CB700 - Page 23

3. SETTING FOR COMMUNICATION
IMCB03-E3
17
!
RS-485 (2-wire system) send/receive timing
The transmission and reception of RS-485 communication are operated by a transmitting wire.
Therefore, the timing of switching should be acted correctly.
Send/receive example in the host computer and controller is show in the following.
Polling procedure
Ｅ
Ｏ
Ｔ
Ｅ
Ｎ
Ｑ
Ａ
Ｃ
Ｋ
Ｎ
Ａ
Ｋ
Ｓ
Ｔ
Ｘ
Ｂ
Ｃ
Ｃ
or
……
……
(
a
)
(
b
)
(
c
)
Host
computer
Controller
Send
data
(Possible/
Impossible)
Send
data
(Possible/
Impossible)
Sending
status
Possible
Impossible
Possible
Impossible
Sending
status
(a):
(Response send time after calling [ENQ] receive) + (Interval time)
(b):
Response send time after BCC send
(c):
(Response send time after acknowledgment [ACK] receive + (Interval time) or
(Response send time after negative acknowledge [NAK] receive + (Interval time)
Selecting procedure
Ｓ
Ｔ
Ｘ
Ｂ
Ｃ
Ｃ
Ａ
Ｃ
Ｋ
Ｎ
Ａ
Ｋ
or
………
(
a
)
(
b
)
Host
computer
Controller
Send
data
(Possible/
Impossible
)
Sending
status
Sending
status
Send
data
(Possible/
Impossible)
Possible
Impossible
Possible
Im
p
ossible
(a):
(Response send time after BCC receive) + (Interval time)
(
b):
Response wait time after acknowledgment [ACK] send or
Response wait time after negative acknowledge [NAK] send