
1.16i/18i/21i-A/B, Power Mate i-D/H, AND 16/18-C OPERATION B-62924EN/04
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Z: The one-scan time within the CNC is determined by expression
(A) shown below:
a1+a2×(N-1)+a3×SIZE≤1000.................................................(A)
a1, a2, a3: Constant parameters
N : Number of communication slave stations
SIZE : DI/DO data size
Table 1.7 Constant Parameters in Expression (A)
CNC
16i/18i/21i-A/B,
Power Matei –D/H
16/18-C
a1 294 282
a2 50 35Constant
a3 1.0 1.2
In expression (A), N and SIZE indicate the number of communication
slave stations and DI/DO data size that can be updated during one
CNC ITP process (8 msec each), respectively.
The procedure for determining N and SIZE is shown below:
<1> Add the DI/DO data size for each communication slave station in
ascending order of station numbers. Each time the DI/DO data
size for a station is added, substitute the cumulative number of
communication slave stations (N) and the DI/DO data size
(SIZE) in expression (A) and check whether the condition is
satisfied.
<2> Increase the values of N and SIZE and obtain the maximum
values of N and SIZE (N
max
and SIZE
max
) that satisfy the
condition for expression (A). The DI/DO data for one to N
max
stations is updated during the first ITP process.
<3> When the value of the left-hand side exceeds 1000, clear the
values of N and SIZE once. Start calculation from step <1> as
the second ITP process.
<4> Perform steps <1> to <3> for all communication slave stations
and count the number of ITP processes (n).
Thus, Z is obtained as follows:
Z : one-scan-time-within-CNC = (n-1) × 8 msec
Example of calculating Z: One-scan time within the CNC)
[Conditions]
• CNC model: 16i/18i/21i-A/B
• Communication slave station settings for the master function:
- DI/DO size set for station No. 3 = 122/122
- DI/DO size set for station No. 4 = 122/122
- DI/DO size set for station No. 5 = 122/122
- DI/DO size set for station No. 6 = 122/122
[Calculation]
• First ITP process
- Calculation for station Nos. 3 and 4:
294+50×(2-1)+1.0×(244+244)=832≤1000
→ N and SIZE indicate the maximum values.