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RS-232C Units Section 6-2
2. The number of bytes of data to be sent is specified when the parameters
for the CMND(194) instruction (CV-series PLCs) or the IOWR instruction
(C200HX/HG/HE PLCs) are set (No. of bytes of command data). It is not
necessary to set this parameter for explicit messages.
3. Before using this command, be sure that the communications status
Transmission Ready Flag (Port 1: bit 00, Port 2: bit 08), allocated in the
Master’s IN Area is ON (transmission enabled). If the command is execut-
ed while the Flag is OFF (transmitting data), and error will occur (error
code 02FF Hex).
RS-232C RECEIVE DATA
READ
Receives data from the specified RS-232C Unit port, and reads the data
stored in the reception buffer. Depending on whether or not the header code
and delimiter code are enabled or disabled, the data read is treated as shown
in the following table. (When the delimiter header is disabled, the number of
bytes set in No. of bytes per frame is read.)
Note H: Header code, D: Delimiter code, N: No. of bytes per frame, Shaded area:
trashed data.
The above explanation is very brief, but if the number. of bytes received after
the delimiter code is set, data after the delimiter code can also be read.
Command Block
Header
code
Delimiter
code
Data read
Disabled Disabled
Disabled Enabled
Enabled Disabled
Enabled Enabled
The "No. of bytes per frame" is read from the
RS-232C Unit's reception buffer, starting with the first
word.
First Second Third
N bytes N bytes N bytes
Data from the RS-232C Unit's reception buffer is
read, from the first word to the delimiter code. (There
is no limit to the amount of data read.)
First Second Third
Data from the RS-232C Unit's reception buffer is
read, from the header code to the "No. of bytes per
frame." In this case, the data before the header code
is discarded
First Second Third
N-1 bytes N-1 bytes N-1 bytes
Data from the RS-232C Unit's reception buffer is
read, from the header code to the delimiter code.
(There is no limit to the amount of data read.) In this
case, the data before the header code is discarded.
First Second Third
Attribute
ID
Service Code
0E
64
Class ID
9400
Instance ID
××00
Destination
node address
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