JUMO DICON 400, Interface Description, Page: 10 / 44

2 Protocol description
10
2.4.1 Timing of a data request
Timing
scheme A data request runs according to the following timing scheme:
t
0
End marker = 3 characters
(the time depends on the baud rate)
t
1
This time depends on the internal processing.
The maximum processing time is 250 msec.
The minimum adjustable response time is required by the RS485 in-
terface of the master, to switch the interface driver over from send
to receive. This parameter is not needed by the RS422 interface.
t
2
This is the time required by the controller to switch from transmit-
ting back to receiving. The master must wait for this length of time
before making a fresh data request. The time must always be main-
tained, even if the new data request is addressed to a different in-
strument.
RS422 interface: t
2
= 1msec
RS485 interface: t
2
= 10msec
H
A minimum response time can be set up in the controller, un-
der the menu item “Interface”. At least this preset time
(0 — 500 msec) must elapse before a response can be sent.
If a smaller value is set, then the response time may be longer
than the set value (because the internal processing time is
longer) and the controller will then respond as soon as the in-
ternal processing is completed. If the time is set to 0 msec,
this means that the controller will respond as fast as it can.
Datenanfrage Master
Slave
t
Datenanfrage
Antwort
t
2
t
0
t
1
t
0
Data request
Data request
Response