IAI America XSEL-S - Manual (Page 31)

2. Specification
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2.2.4 Input and Output Timing (Fieldbus Type)
The response time (Time it takes RC controller to respond back to XSEL controller's query) can be
calculated by the formula below:
Response time [msec] = Yt + Xt + 2 × (Ft + Mt) + Command processing time
Yt : SEL Program ĺ RC Controller transmission delay time… 2ms or more (It may increase due to
number of executed SEL programs or
number of effective axes.)
Xt : RC Controller ĺ SEL Program transmission delay time… 2ms or more (It may increase due to
number of executed SEL programs or
number of effective axes.)
Ft : Fieldbus Link Cycle Time
x In the case that the Multi-axis (MSEP or MSCOM) units only are connected:
Ft = Ȉ {0.316 + 0.076 × (T
HBYTE
+ T
ABYTE
× Ni)} + 1.0
Ȉ : Total No. of the controller connected multi-axis (MSEP or MSCOM) units
(= No. of Connected Nodes)
T
HBYTE
: Number of header domain bytes. Fixed to 16
T
ABYTE
: Number of bytes for each axis.16 for method to use position data in X-SEL, and 8 for
method to use position data in RC
Ni : No. of connected axes of the multi-axis (MSEP or MSCOM) units per controller
x When connecting only CON single axis (A/PCON, SCON-CA)
Ft = 1.532 × N + 1.0 (Method to use position data in X-SEL)
Ft = 0.556 × N + 1.0 (Method to use position data in RC)
N : Number of connected nodes (= number of connected axes)
Mt : Modbus Line Time (Added only for MSEP or MSCOM): 10ms
Caution : x Regarding the response time of Fieldbus Type, because the communication data
length of DeviceNet is 8 bytes, the communication speed becomes slow if the
number of communication bytes for each node exceeds 8 bytes. For instance,
even though the communication size in the method to use the position data in RC
is 80 bytes for input and output, for MSEP (8-axis connection: 1 node), it is 20
[ms], but for CON single axis (10-axis connection: 10 nodes), it iis 9 [ms].
x Yt increases with the facts such as the number of SEL programs executed at the
same time or the number of effective axes in the RC Gateway Funciton.
x When a communication error is generated, the Fieldbus Link Time Ft and Modbus
Link Time Mt may be longer since such actions as a retry will take place.