User`s manual

Graphic Operation Terminal F930GOT Additional Functions (V 2.20/3.00 or later) 15
15-12
15.5.2 Communication procedure
• When two or more GOT units are connected (with station No.)
Communication between the GOT units and the host unit is performed in the procedure in
which the host unit sends a command with the station No., and the GOT having the speci-
fied station No. sends back a response to it.
At first, the 1st GOT unit directly connected to the host unit performs the following to a com-
mand sent from the host unit.
- When receiving a command to itself, the 1st GOT unit sends back a response to it.
Until sending back is completed, the 1st GOT unit does not receive any command from
the host unit.
- When receiving a command to another GOT unit, the 1st GOT unit sends the command
from the host unit as it is to the 2nd GOT unit connected to another port, and waits for a
response to it.
- When receiving a response, the 1st GOT unit immediately sends the response as it is
to the host unit.
Until sending of the response to the host unit is completed, the 1st GOT unit does not
receive any command from the host unit.
- The timeout time for response is 5 seconds.
If a response is not given within 5 seconds after sending a command to the 2nd GOT
unit, the 1st GOT unit is ready for receiving a command from the host unit.
The 2nd GOT unit and later GOT units perform the same processing as the 1st GOT unit.
As to notification of interrupt, when a certain event occurs in itself or receiving an interrupt
code from another GOT unit, the GOT unit immediately sends the interrupt code to the host
unit.
However, while sending a response to the host unit, the GOT unit waits until sending is fin-
ished, then sends the interrupt code after sending is finished.
The interrupt code and the event type correspond each other in the same way as connec-
tion on the one-to-one basis. If two or more GOT units share the interrupt codes, you
should set them properly so that they do not overlap.
Host
1st GOT
Command
to 1st GOT
Response
Response
Command
to 2nd GOT
2nd GOT
Command
to 2nd GOT
Response
Command
to 3rd GOT
3rd GOT
Response
Command
to 3rd GOT
Command
to 3rd GOT
Response
Response
Host
1st GOT
Response
2nd GOT
Command
to 2nd GOT
3rd GOT
Response
Command
to 2nd GOT
Command
to 1st GOT
Response
Interrupt
Event occurs.
Interrupt
Interrupt
If receiving an interrupt code from another GOT
while sending back a response, the GOT sends
the interrupt code after finishing sending back of
the response.
If receiving an interrupt code from another GOT in
any status except sending back of a response
(while receiving a command, for example), the
GOT immediately sends the interrupt code.
If an event occurs while sending
back a response, the GOT sends
an interrupt code after finishing
sending back of the response.