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5. NON
PROCEDURE
PROTOCOL
COMMUNICATIONS
MELSEC QnA
Non procedure protocol handshake inpuVoutput signals
The signals that send the data output from the sequence program to the external device
and the signals that detect the arrival of data from the external device and enable the
sequence program to read the data when the non procedure protocol is used
to
send and
receive data are called "handshake signals". These signals are necessary with the non
procedure protocol.
The following shows the handshake inputloutput signals.
PC CPU
L
3ternal device
External device
L
PC CPU
Signal
{no (Request to Send)
(n2 (Sending)
(no (End of Transmission)
Xn3
(Request to Read Receivt
Data)
Ynl
(End of Reading of Receivt
Data)
Turned
OFF
by
the
program:
\
A
Turned ON/OFF
bv
\ I
the QC24.
Turned
OFF by
Turned
ON
by
the QC24.
Turnec OFF by
t - x
the QC24.
-
Turned ON bv
( 7
the
QC24.
Turned OFF by
the program.
Turned ON by
the program.
In this guidebook, AJ71 QC24 dedicated instructions are used to send and receive data in
the non procedure protocol mode.
Data transmission from PC CPU
:
OUTPUT instruction (Section 5.5)
PRR instruction (Section 5.7.2)
Data reception from external device
: INPUT instruction (Section 5.6)
Registering of user frame to EEPROM
:
PUTE instruction (Section 5.7.3)
By using dedicated instructions, data can be sent and received without being aware of
the handshake signals and inputloutput signals above and the buffer memory address.
The data sendlreceive programs are also simple.
5 - 7
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