Omron CQM1-ARM21 Operation Manual page 20

Introduction
Security
Performance
6
Master
sends
Master Request
Slave
receives
Master Request
A request or response will be judged invalid if it contains one of the following
types of error:
Start bit error The initial pulse is not negative.
Alternating error Two consecutive pulses do not have different polarity.
No information Pulses are not detected in periods of
Parity error The sum of all information bits is not even.
End bit error The last pulse is not positive.
Length error Pulses are detected during the master or slave pause.
Upon an invalid or missing slave response, a master station will retry to
access the slave. If this fails, the slave will be taken out of the list of active
slaves. The master will cyclically try to re-initialise the slave in the inclusion
phase.
The cycle time of an AS-Interface network depends on the number of slaves
that the master has to exchange I/O data with. The AS-Interface specification
defines the maximum bus cycle time as follows:
n * Master request = n * (14 Bit) = n * 84 µ s
+ n * Master pause
+ n * Slave response = n *
+ n * Send pause
= T cycle
where n is the number of all AS-Interface requests during data exchange in
the AS-Interface cycle and in the inclusion phase, including one repetition. In
normal operation, n will be the number of slaves plus 2.
With less than 31 slaves, the AS-Interface cycle time will be shorter. In
principle, each slave less will decrease the cycle time by 156 µs, but the
master is allowed to lengthen the send pause up to 500 µs, as long as the
total cycle time does not exceed the stated maximum.
To calculate the CQM1-ARM21's cycle time, see 3-3, Performance.
Transaction
receives
Slave Response
sends
Slave Response
Master Pause
(2,5 to 5,5 bit times)
(3 Bit) = n * 18 µ s (synchr. slave) =
= n *
(7 Bit) = n * 42 µ s
(2 Bit) = n * 12 µ s (min.)
= n *
= n * (26 Bit) = n * 156 µ s (min.)
Section 1-1
Slave Pause (1 -2 bit times)
Send Pause
sends
Master Request
receives
Master Request
time
+ µ
1 0 .
( * ) n 6 s
.
−
0 5 .
if n = 33
2722 µ s
=
594 µ s
1386 µ s
=
396 µ s
=
5148 µ s
=