JUMO DICON 400, Interface Description, Page: 8 / 44

2 Protocol description
8
2.3 Instrument address
The addresses of the slaves can be set from 1 to 31. The instrument ad-
dress 0 is reserved.
There are two distinct types of data exchange:
Query Data request/instruction from the master to a slave, via the correspond-
ing address. The slave that is accessed will respond.
Broadcast An instruction from the master to all slaves, via address 0. The slaves in
the system do not respond. For example, a certain setpoint can be
transmitted to all slaves. In this case, the correct acceptance of the val-
ue by the slaves should be checked by a subsequent read-out of the
setpoint.
A data request using instrument address 0 is meaningless.
2.4 Timing of the communication
The start and end of a data block are identified by transmission pauses.
The maximum permitted interval between two consecutive characters is
three times the time for transmitting one character.
The character transmission time (time for transmitting a character) de-
pends on the baud rate and the data format that is used (stop bits and
parity bit).
If the data format has 8 data bits, no parity bit and one stop bit, then:
character transmission time [msec] = 1000 * 9 bits/(baud rate)
For the other data formats:
character transmission time [msec]
= 1000 * (8 bits+parity bit+stop bit(s))/(baud rate)
Procedure
H
The RS422/485 interface can access a maximum of 254
slaves.
Data request from master
transmission time = n characters * 1000 * x bits/(baud rate)
marker for end of data request
3 characters * 1000 * x bits/(baud rate)
processing the data request by the slave (max. 250msec)
Response of slave
transmission time = n characters * 1000 * x bits/(baud rate)
marker for end of response
3 characters * 1000 * x bits/(baud rate)