Table of Contents
Advertisement
1.
GENERAL DESCRIPTION
MELSEC-A
(This is the on-demand function of the AJ71 C24. It is available
only when one computer is connected t o one PC CPU.)
*
I: The dedicated protocols consist of four different protocols.
The term 'dedicated protocols' used i n this manual is the col-
lective term for these protocols.
(2) Communications in the no-protocol/bidirectional modes
Either the no-protocol mode or the bidirectional mode can be set.
(a) Communications in the no-protocol mode
1) Data communications can be initiated by a PC CPU
Data communications can be initiated by a computer or any PC
CPU. Data can be transmitted from a PC CPU to an external
device by using the TO instruction in the sequence program to
write data t o the buffer memory.
Data transmitted from an external device can be read by a PC
CPU using the FROM instruction in the sequence program.
4
The following example shows a system with a printer, CRT and
keyboard terminal connected in a 1:l ratio. Data can be output
from the buffer memory to the printer or a CRT display using the
TO instruction.
Data input from the keyboard to the buffer
memory can be read using a FROM instruction from the PC CPU.
2) Receiving data length can be set to variable or fixed:
The Length of the data transmitted from an external device and
received by the PC CPU can be set t o variable or fixed.
4
P C C P U
i) Receiving variable-length data:
AJ71C24
T O instruction
Data receive stops when the receive completed code set by
the user is received.
Printer. CRT, computer
FROM
instruction
-
ii) Receiving fixed-length data:
Computer, keyboard
Data receive stops when the fixed length of data set by the
user is received.
Both the receive completed code and the receive-completion
data length can be freely set by the user.
3)
Variable communications memory area
The user memory area can be allocated to suit the purpose and
application of the data transmission.
Advertisement
Table of Contents
