2
0
1
8
-0
7
18
Appendix
Transmission time
The transmission time is based on the AS-Interface specification. The AS-Interface transmits
data in 4-bit packets. At values greater than 4 bits, the quantity of data is divided into smaller
values and then transmitted to a com unit over several cycles. If several channels are
transmitted per slave, the number of cycles increases. The transmission time is the time
required to fully transmit a digital data volume to the com unit. In the profile 7.3, seven frames
are required per channel.
The duration of a cycle depends on the number of occupied addresses in the AS-interface
network. An address is considered occupied if one of the following configurations apply:
■
A standard address is assigned (e. g.
1
)
■
An A- or B-Address is assigned (e. g.
1A
or
1B
)
■
An A- and a B-Address are assigned (e. g.
1A
and
1B
)
When calculating the cycle time, each of these configurations assumed to be
one
occupied
address.
Cycle time = 150
µ
s * ([Number of occupied addresses] +2)
The transmission time is 7 cycles:
Transmission time = 150
µ
s * ([Number of occupied addresses] +2) * 7
Example:
In a network, the addresses of 1A, 1B, 2A and 3 are assigned. For the calculation of the
transmission time this corresponds to 3 occupied addresses. Thus we have:
Transmission time = 150
µ
s * (
3
+2) * 7 = 5,25 ms
■
4 occupied addresses: Transmission time = 6,3 ms
■
31 occupied addresses: Transmission time = 35 ms
