Appendix 4 Processing Time; Link Scan Time - Mitsubishi Electric MELSEC iQ-R Series User Manual

Appendix 4

Link scan time

The link scan time is a time taken for the following sequential operation in the I/O communication whose connection type is
polling or bit strobe: The RJ71DN91 (master node) issues a request, the request is transmitted to all slave nodes and
responses are waited, and the RJ71DN91 issues another request.
The link scan time can be calculated with the following calculation formula.
LS = (TIn + TOn + 0.097) + 0.222  BR + 1.0 [ms]
LS: Link scan time [ms]
TIn: Receive data transfer time from n-th slave node [ms] ( Page 95 Calculating TIn)
TOn: Transmit data transfer time to n-th slave node [ms] ( Page 95 Calculating TOn)
: Indicates that the values in () is added to all slave nodes. (except for reserved nodes)
BR: Coefficient depending on the communication speed (125kbaud = 4, 250kbaud = 2, 500kbaud = 1)
• The concept of the link scan time is not applied to the change of state and cyclic type I/O communication.
• For the multi-master configuration, the link scan time may be longer than the calculated result depending on
the communication timing with other master nodes.
Calculating TIn
■When the receive data length from the n-th slave node is 8 bytes or less
TIn = BT + BTa  Receive data length (byte) [ms]
BT, BTa: Coefficient depending on the communication speed ( Page 95 Coefficient BT, BTa depending on the
communication speed)
■When the receive data length from the n-th slave node is 9 byte or more
TIn = (BT + BTa  8 + 0.190)  a + {BT + BTa  (b + 1) + 0.450} [ms]
BT, BTa: Coefficient depending on the communication speed ( Page 95 Coefficient BT, BTa depending on the
communication speed)
a: Value obtained when the receive data length is divided by 7 (round down the decimal)
b: Remainder obtained when the receive data length is divided by 7
Calculating TOn
■When the transmit data length to the n-th slave node is 8 byte or less
TOn = BT + BTa  Transmit data length (byte) [ms]
BT, BTa: Coefficient depending on the communication speed ( Page 95 Coefficient BT, BTa depending on the
communication speed)
■When the transmit data length to the n-th slave node is 9 byte or more
TOn = (BTBTa  8 + 0.130)  c + {BT + BTa  (d + 1) + 1.2} [ms]
BT, BTa: Coefficient depending on the communication speed ( Page 95 Coefficient BT, BTa depending on the
communication speed)
c: Value obtained when the transmit data length is divided by 7 (round down the decimal)
d: Remainder obtained when the transmit data length is divided by 7
Coefficient BT, BTa depending on the communication speed
The following table shows the coefficients BT and BTa depending on the communication speed.
Coefficient
BT
BTa
Processing Time
125kbaud
0.376
0.064
250kbaud
0.188
0.032
500kbaud
0.094
0.016
APPX

Appendix 4 Processing Time

A
95