12.4.11
Write Bytes Function (4401)
This operation can be used to transmit one or more characters to the remote device
through the specified serial port. The character(s) to be transmitted must be in a word
reference memory . They should not be changed until the operation is complete.
Up to 250 characters can be transmitted with a single invocation of this operation. The
status of the operation is not complete until all of the characters have been transmitted or
until a timeout occurs (for example, if hardware flow control is being used and the remote
device never enables the transmission).
12.4.11.1
Example Command Block for the Write Bytes
Function
VALUE
(decimal)
VALUE
(hexadecimal)
MEANING
address
0006
0006
Data block length (includes characters to send)
a1
0000
0000
NOWAIT mode
a2
0008
0008
Status word memory type (%R)
a3
0000
0000
Status word address minus 1 (%R0001)
a4
0000
0000
Not used
a5
0000
0000
Not used
a6
4401
1131
Write bytes command
a7
0030
001E
Transmit time-out (30 seconds). Refer to the
following note.
a8
0005
0005
Number of bytes to write
a9
25960
6568
‘h’ (68h), ‘e’ (65h)
a10
27756
6C6C
‘l’ (6Ch), ‘l’ (6Ch)
a11
111
006F
‘o’ (6Fh)
Although printable ASCII characters are used in this example, there is no restriction on
the values of the characters which can be transmitted.
12.4.11.2
Operating Notes
Note
Specifying zero as the Transmit time-out sets the time-out value to the amount of
time actually needed to transmit the data, plus 4 seconds.
Caution
If an Initialize Port (4300) COMMEQ is sent or a
Cancel Operation (4399) COMMREQ is sent in
either Cancel All or Cancel Write mode while this
COMMREQ is transmitting a string from a serial
port, transmission is halted. The position within the
string where the transmission is halted is
indeterminate. In addition, the final character
received by the device the CPU is sending to is also
indeterminate.
Serial I/O / SNP / RTU Protocols
GFK-1503E User Manual 245
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Summary of Contents for VersaMax PLC
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