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9. COMMUNICATIONS IN THE NO-PROTOCOL MODE
MELSEC-A
9.5
Receiving Data i n the No-Protocol Mode (External Device
-
AlSJ71C24)
(1)
Data receive area
The A1 SJ71C24 stores the received data length and received data in the
data receive area.
With default setting, buffer memory area 80H to FFH is allocated as the
receive area.
This area may be changed as needed.
See Section 6.4.5 for the
procedure to change the data receive area.
For example, if the data to be received is greater than the AlSJ71C24
receive area (127 words in default setting), data is received in more than
one transmission.
It is advisable to set as "data receive area" is larger than "received data
length"
r - - -
Address
(default)
Buffer memory
Received data length
. . . . . . . . . . . . .
to
Received data
FFH
The unit (wordibyte) of received data length
depends on the setting with the wordibyte setting
area (address 103H).
The actual length of received data is written
when the receive completed code is received or
the set length of data has been received.
Received data is stored sequentially from the
lowest address until the completed code is
received or the set length of data has been
received.
(2)
Reading received data
There are two ways of making a request to read the received data:
By receiving the receive completed code (data receive in variable
length), and
.
By receiving the set length of data (data receive i n fixed length).
(a) By receiving the receive completed code (variable length)
The AlSJ71C24 makes a request to read the received data to the
sequence program when it receives the receive completed code,
predetermined by the user and set to the AlSJ71 C24 buffer memory.
The default receive completed code is CR, LF (ODOAH), but this may
be changed to any value in the range of OOOOH to OOFFH. (For the
procedure to change the read completed code, see Section 7.4.1 .)
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