Mitsubishi Melsec-L Series User Manual page 192

(2) Arrangement of receive data
C24
Receive area
(buffer memory)
Receive
5
(00 )
data count H
B
(42 )
H
D
(44 )
H
Receive
F
(46 )
data
H
1
(31 )
H
3
(33 )
H
(3) Contents of receive data
11 - 6
The following example illustrates the arrangement of data received from the
external device when it is stored in the receive area.
1) The receive message is stored to the C24 buffer memory (receive data
storage area).
2) The data is stored to the receive data storage area in the order of low
address (L) (H), next address (L)
If the received data is "ABCDEFG123", it will be stored as shown below (for
the CH1 side):
(05 )
Data
H
length
A
ENQ (0005 )
(41 )
H
H
L H
C
(43 )
H
05 00
H H
E
(45 )
H
G
(47 )
H Transmission data (Response message)
2
(32 )
H
When the data length unit is in bytes, 00
last data storage position in the receive area when the data length of the
message is an even byte.
The contents of receive data, including the receive data as indicated in
Section 11.2.2, are explained below.
(a) Control codes
The types of control codes are shown in the table below.
Signal Code
name (hexadecimal)
ENQ 05
H
ACK 06
H
NAK 15
H
1) For data communication from the external device to the C24
The C24 checks and processes the control code received.
It cannot be read from the sequence program.
2) For data communication from the C24 to the external device
The control code to be transmitted is added by the C24.
11 DATA COMMUNICATION USING THE BIDIRECTIONAL PROTOCOL
Receive data
A B C D E F G
41 42 43 44 45 46 47
H H H H H H H
ACK
06
H
(Normal completion)
Contents
Enquiry Code for starting data transmission.
Response code to the opposite side when data was
Acknowledge
received normally.
Response code to the opposite side when data could
Negative
not be received normally. (Error code is sent
Acknowledge
immediately after the response code.)
(H).
Sum
1 2 3
check
code
L H
77 02
31 32 33
H H
H H H
External device
is stored in the higher byte of the
H
Application
11 - 6