Omron SYSMAC CJ - REFERENCE MANUAL 08-2008 Reference Manual page 1049

Serial Communications Instructions
Related Flags and Words
If ER signal control is specified in C, bit 15 of S will be used as the ER signal.
If RS and ER signal control is specified in C, bit 15 of S will be used as the RS
signal and bit 14 of S will be used as the ER signal.
TXDU(256) uses a logical port (because it sends an internal FINS command)
to output a send sequence command to the Serial Communications Unit (ver-
sion number 1.2 or later). Since SEND(090), RECV(098), CMND(490),
PMCR(260), and RXDU(255) also use logical ports 0 to 7, TXDU(256) cannot
be executed for a logical port if that logical port is already being used by one
of those instructions or another TXDU(256) instruction.
To ensure that TXDU(256) is not executed while the logical port is busy, pro-
gram the port's Communications Port Enabled Flag (A20200 to A20207) as a
normally open condition.
TXDU(256) can not be executed while the TXDU Instruction Executing Flag
(bit 5 of n+9 or n+19, where n = CIO 1500 + 25
ensure that another TXDU(256) is not executed for the port before the first
TXDU(256) is completed, program the port's TXDU Instruction Executing Flag
as a normally closed condition.
An error will occur and the Error Flag will turn ON in the following cases.
• The Communications Port Enabled Flag for the specified logical port is
OFF when TXDU(256) is executed.
• The value of C is not within range.
• The value for N is not between 0000 and 0100 hex.
Note Depending on the external device, it might be necessary to set a send delay
when sending data with TXDU(256). It a send delay is required, set or adjust
the delay time in the allocated DM Setup Area.
The following PLC Setup settings and Auxiliary Area flag can be used as
required when executing TXD(236).
DM Setup Area Settings
(m = D30000 + 100
Setup Area word
Port 1 Port 2
m+2 m+12
CPU Unit
TXDU
TXDU
unit number)
Bit Name
15 No-protocol Mode Send
Delay Specifier
0 to 14 No-protocol Mode Send
Delay Time
Section 3-24
unit number) is ON. To
Settings
0: Default (0 ms)
1: Use delay in bits 1 to 14.
0000 to 7530 hex
0 to 300,000 ms decimal
(in 10-ms units)
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