4. FUNCTIONS
MELSEC-A
4-10
4.3.2
Buffer memory detailed description
(1)
INPUT area
Either normal service mode or extended service mode can be selected via the mode switch on
the main unit.
(a)
Normal service mode (MODE switch : No. 0)
This is the area that stores the input data from the slave station.
This area is fixed to an allocation of 32 bytes (16 words) per station for a total of 60 stations
worth. This input area configuration is as follows.
Example : When the input data length for the first station is set to 29 bytes and that for the
second station to 32 bytes
Address
Address
1st station input data
2nd station input data
n th station input data
60th station input data
1st station 2nd byte
1st station 4th byte
1st station 1st byte
1st station 3rd byte
1st station 29th byte
b15
b0
2nd station 2nd byte
2nd station 4th byte
2nd station 1st byte
2nd station 3rd byte
2nd station 30th byte
2nd station 32nd byte
2nd station 29th byte
2nd station 31st byte
b15
b0
(Upper byte)
(Lower byte)
: Free area (00h)
*1: Since the data area is fixed to 32 bytes,
all unused areas will become free.
*1
*1
0/0h
15/Fh
16/10h
31/1Fh
944/3B0h
959/3BFh
0/0h
1/1h
14/Eh
15/Fh
16/10h
17/11h
30/1Eh
31/Fh
Point
The input data of the slave station, which was disabled from communication during normal
communication and whose corresponding bit of the communication status area*1 turned ON (1),
is not stored into the input area of the AJ71PB92D/A1SJ71PB92D.
In the input area of the corresponding slave station, the data before communication failure is
held.
*1: Indicates the area of buffer memory addresses 2113 (841
H
) to 2116 (844
H
) in the slave status
area.