7-2
Section
Using Message Communications
89
Reference When sending explicit messages, set the response monitoring time in C+5 to
0014 Hex (2 seconds) or higher. If a shorter time is set, communications may still
be busy when the next command is sent after a timeout occurs.
The maximum number of bytes that can be transferred (shown above) is the
maximum number of bytes allowed with CMND(194). The actual number of by-
tes that can be sent or received depends upon the explicit message.
Normally, CMND(194) is used with the following flags ANDed as executions
conditions to ensure that any previous network communications operation has
completed before CMND(194) is executed. The Port Enabled Flag for the com-
munications port and the Message Enabled Flag for the Master Unit are general-
ly programmed as follows:
SEND, RECV, or CMND
Execution
condition
Port Enabled
Flag
Message
Enabled Flag
Communications Flags
The following table shows the flags that are normally used when executing
CMND(194).
Flag
Functions
Port #0 to #7
Enabled Flags
(A50200 to A50207)
Enabled Flags A50200 to A50207 are OFF during
communications instruction execution for ports #0 to #7,
respectively, and turn ON when execution has
completed (regardless of whether or not an error has
occurred).
Do not start a communications instruction for a port
unless the corresponding Enabled Flag is ON.
Port #0 to #7
Execution Error Flags
(A50208 to A50215)
Execution Error Flags A50208 to A50215 turn OFF
following normal completion of a communications
instruction (i.e., after reception of response signal) for
ports #0 to #7, respectively. These flags turn ON after an
unsuccessful communications instruction attempt.
Execution Error Flags will maintain status until the next
communications instruction. They will turn ON when the
next communications instruction is executed even if an
error occurred for the last instruction.
Error types:
Time-out error (command/response time greater than
the response monitoring time set in the control words)
Transmission data errors
Message
Communications
Enabled Flag in the
Master Unit status area
(bit 12 in CIO 1500 +
(25 x unit No.))
The Communications Enabled Flag turns OFF when
message communications are not possible for the
Master Unit due to detection of Bus Off or other errors.
This flag is ON when message communications are
possible.
Note The behavior of the Message Communications Enabled Flag in the CVM1/CV-
series PCs is different from the behavior in the C200HX/HG/HE PCs.
Reference In the CVM1/CV-series PCs, the 8 ports can be used independently to execute
network instructions SEND(192), RECV(193), and CMND(194).
Communications Flag Operation
The relationship between the the Message Communications Enabled Flag and
the NS indicator is shown in the following table.
Using CMND(194)
