Azbil F4Q, User Manual

Page: 33 / 76

4-17
Chapter 4. CPL Communication
„
Timing for response messages
The response time of this device, from the time when the master station finishes
sending the instruction message until the time when it begins to receive the
response message from the slave station, is shown below.
Minimum: 20 ms, maximum: 2000 ms
Therefore, monitoring of the response message should begin within 20 ms after an
instruction message is sent, and the response should be monitored for 2000 ms or
longer.
Generally, when a response time-out occurs, the instruction message is resent.
„ RS-485 driver control timing
When the transmission/reception on the RS-485 3-wire system is directly
controlled by the master station, pay attention to the following timing:
(Enable)
(Enable)
(Disabled)
(Disabled)
Master station
driver control
Slave station
driver control
Transmission line
(Instruction message)
Valid
data
Valid
data
End of master station transmission End of slave station transmission
(Response message)
(1)
(4)
(2) (3)
(1) Time from completion of master station transmission to TX disabling by
master station driver: Time (2) max.
(2) Time from completion of slave station reception to TX enabling by slave
station driver: 20 ms min.
(3) Time from completion of slave station transmission to TX disabling by slave
station driver: 1 ms max.
(4) Time from completion of master station reception to TX enabling by master
station driver: Time (3) min.
Handling Precautions
•
The time from when the master station finishes sending the instruction
message to when the slave station starts transmitting the response message
will vary according to the amount of data to be read or written. If a faster
response from the slave station is required, reduce the amount of data to be
read or written by one message.
•
When multiple messages are sent consecutively, a new message should be
sent only after the response for the previous message from this product is
received.
4 - 5 Timing Specifications