AS-Interface Performance with BMX EIA 0100 Bus Master
Original instructions
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Introduction
The AS-Interface bus is independently managed by the master. It exchanges data on each cycle with each slave device configured on the bus (in ascending order of slave address number).
Scanning Time
Scanning time t represents the exchange time between the master and n slaves (31 maximum on each bank).
t = (2 + number of active slaves) * 0.156 ms
When two slaves on bank A and bank B have the same address, each slave in the pair is scanned every two cycles.
Thus, for 31 extended address slaves on bank A + 31 extended address slaves on bank B, the scanning time is 10 ms.
Response Time
The response time T represents the AS-Interface cycle time.
This includes:
Example with Digital Slaves
The table below shows three examples of the response time, T, for a PLC task lasting 10 ms and 30 ms.
This time, T, is for a bus loaded with 31 slaves operating normally and without Combined Transaction support:
PLC task
Typical response time
Maximum response time
10 ms
40 ms
65 ms
30 ms
70 ms
105 ms
Example with Combined Transactions Slaves
For Combined Transaction slaves, the performance for a 10 ms PLC task is:
CT Type
Profile
Bus Transmission Tine
Typical Response Time
Maximum Response Time
CTT1
S-7.3
35 ms per channel
100 ms per channel
100 ms per channel
CTT2
S-7.A.7
10 ms
50 ms
70 ms
CTT3
S-7.A.A
20 ms
70 ms
90 ms
CTT4
S-7.A.8
S-7.A.9
15 ms per channel, 14 bits
20 ms per channel, 12 bits
60 ms per channel, 14 bits
70 ms per channel, 12 bits
80 ms per channel, 14 bits
90 ms per channel, 12 bits
CTT5
S-6.0.•
5 ms
40 ms
60 ms