Mitsubishi-electric QJ71C24N Manuel d'utilisateur télécharger pdf (Page 128)

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MELSEC-Q

6 DATA COMMUNICATION USING THE NON PROCEDURE PROTOCOL

(2) Receive data list

The following describes the data list when data received from an external device

is stored to the receive area.

1) The receive message is stored to the Q series C24 buffer memory (receive

data storage area).

2) The data is stored to the receive data storage area in low address (L)

(H),

next address (L)

(H) order.

Under the following conditions, when the receive data count is an odd

byte, 00

is stored in the upper byte of the final data storage position:

• When the unit for the received data count is designated in bytes.

• When data reception is performed using the receive complete code.

(Example) When receive arbitrary data area "ABCDEFG123" was stored

(The receive area is the default value.)

600

601

602

603

604

605

606

(B)

(C)

(D)

(E)

(F)

(G)

(1)

(2)

(3)

"321GFEDCBA"

Head

……

(A)

Q series C24

( 1)

From external

device

OS area

The receive data is stored in low

address (L)

→ (H), next address

(L)

→ (H) order in the order in which

it is received.

Receive data storage area

Receive data count storage area

5 or 10

Buffer memory

CH1

address

1 The OS area of the Q series C24 shown in the above diagram is the

memory (8448 bytes) that temporarily stores the data to be received while a

request for the reading of the receive data is being made to the PLC CPU.

(The user cannot read the receive data in the OS area).

When the sequence program finishes reading the receive data in the

buffer memory in response to the read request, the receive data in the OS

area, and any succeeding receive data, is stored successively in the

receive area of the buffer memory when the next read request is issued.

Also, when the OS area's free space, which stores the receive data, is

reduced to 64 bytes default value or less, a request to discontinue data

reception from the external device is issued by the following transmission

control (the RS signal does not turn OFF):

• When DTR control is set, the DTR signal turns OFF.

• When DC1/DC3 control is set, DC3 is sent.

When there is no more free space in the OS area to store receive data,

an SIO error occurs and the SIO information bit in the communication

error information storage area (address: 201

/202

) in the buffer

memory turns ON. In that case, succeeding receive data is discarded

until a free space becomes available in the OS area.

For more details on the transmission control, see Chapter 7 of the

User's Manual (Application).

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Mitsubishi-electric QJ71C24N Manuel d'utilisateur Page 128

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