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)
address +1 0000 0000 NOWAIT mode
address +2 0008 0008
Status word memory type (%R)
address +3 0000 0000
Status word address minus 1 (%R0001)
address +4 0000 0000 Not used
address +5 0000 0000 Not used
address +6 4401 1131
Write bytes command
address +7 0030 001E
Transmit time-out (30 seconds). Refer to the
following note.
address +8 0005 0005
Number of bytes to write
address +9 25960 6568
‘h’ (68h), ‘e’ (65h)
address +10 27756 6C6C
‘l’ (6Ch), ‘l’ (6Ch)
address +11 111 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
For public disclosure
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