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Network Instructions
Section 5-29
sion is specified, responses will not be returned and transmissions will not be
retried.
An error will occur if the amount of response data exceeds the number of
bytes of response data set in C+1.
If the Network Instruction Enabled Flag (AR 0209) is OFF when CMND(––) is
executed, the instruction will be treated as NOP(00) and won’t be executed.
An error will occur and the Error Flag will be turned ON.
If the Network Instruction Enabled Flag (AR 0209) is ON when CMND(––) is
executed, the Network Instruction Error Flag (AR 0208) and Network Instruc-
tion Enabled Flag (AR 0209) will be turned OFF, the Network Instruction Com-
pletion Code will be set to 00, and the FINS command will be issued to the
node(s) on the network.
The destination node(s) will be located through the routing tables registered in
the network PCs. (Routing tables indicate the routes to other networks in
which destination nodes are connected.)
Only one network instruction may be executed at one time. To ensure that a
second network instruction isn’t executed until the first is completed, program
the Network Instruction Enabled Flag (AR 0209) as a normally open condi-
tion.
Never change the control data (C through C+5) while FINS command is being
processed and the Network Instruction Enabled Flag is OFF.
Noise and other factors can cause the transmission or response to be cor-
rupted or lost, so we recommend setting the number of retries to a non-zero
value which will cause CMND(––) to be executed again if the response is not
received within the response monitoring time.
CMND(––) operates just like SEND(90) if the FINS command code is 0102
(MEMORY AREA WRITE) and just like RECV(098) if the code is 0101 (MEM-
ORY AREA READ).
Examples
When IR 00000 and AR 0209 (the Network Instruction Enabled Flag) are ON
in the following example, CMND issues FINS command 0101 (MEMORY
AREA READ) to node number 3 in the local network.
The MEMORY AREA READ command reads 10 words from DM 0010 to
DM 0019. The response contains the 2-byte command code (0101), the 2-
byte completion code, and then the 10 words of data, for a total of 12 words or
24 bytes.
The command will be issued again up to 3 times if a response is not received
within ten seconds.
