Ethernet Units Operation Manual

96
Sending Commands From a Host Computer Section 5-4
Example Calculations The following example shows calculations for receiving 256 words between
two PC nodes using RECV(098). The local node’s CPU cycle time is 10 ms,
and the remote node’s CPU cycle time is 15 ms. Calculations are shown in the
following table.
5-4 Sending Commands From a Host Computer
Commands and responses sent from host computers must be in the formats
described in this section and must provide the proper FINS header informa-
tion. These formats can also be used to decode commands and responses
received from other network nodes.
5-4-1 Designating Remote Addresses
UDP sockets are used when sending FINS commands from a host computer
to a PC. This section provides examples of addressing remote PCs from the
host computer for communications.
Note 1. The FINS UDP port number at the Ethernet Unit is set to the default of
9600. It can be changed in the CPU Bus Unit System Setup, but the same
FINS UDP port number must be set for all of the Ethernet Units on the
same Ethernet network.
2. Even if the Ethernet network is comprised of multiple segments, set the
same value for the FINS network number.
Item Calculation
CPU Bus Unit service cycle (local node) PC cycle time = 10 ms
CPU Bus Unit service processing time
(local node)
1 ms
Transmission processing time (command) 3 ms
Reception processing time (command) +
Remote node service cycle + CPU Bus
Unit service processing time (remote
node)
3 + 15 + 1 = 19 ms
CPU data read processing time (remote
node)
256 x 0.02 + 20 = 25.12 → 30 ms
Service processing 1 ms
Transmission processing time (response) 256 x 0.011 + 3 = 5.816 ≅ 6 ms
Reception processing time (response) +
Local node service cycle + CPU Bus Unit
service processing time (local node)
(256 x 0.011 + 3) + 10 + 1 = 16.816 ≅
17 ms
CPU data set processing (local node) 256 x 0.02 + 20 = 25.12 ≅ 25 ms
Total 10 + 1 + 3 + 19 + 30 + 1 + 6 + 17 + 25 =
112 ms