Mitsubishi MELSEC Q Series Reference Manual page 216

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3 WHEN COMMUNICATING USING THE QnA COMPATIBLE 3E/3C/4C FRAMES OR 4E FRAME
(e) Number of clusters to be read
This value designates the number of clusters within the drive memory
range who are to be read. It is designated in multiples of 16 (10
hexadecimal representation).
1) Data communication in ASCII code
A number of clusters in the range from 10
converted to a 4-digit (hexadecimal) ASCII code and sequentially
transmitted beginning from the most significant digit ("0").
2) Data communication in binary code
The 2-byte value that indicates the number of clusters in the range
from 10
the low byte (L: bits 0 to 7).
3) When the drive memory is defragmented, the number of clusters to
read does not have to be designated.
POINT
Designate the number of clusters to read within the range of the usable memory
size after formatting the drive to be read from. (For the number of bytes in a cluster,
refer to Section 3.7.)
Number of clusters = Usable memory size / Number of bytes in one cluster (4096
or 512)
(f) Free cluster table
This data section (indicating the status of cluster usage) is returned to the
external device when the drive memory usage status is read.
1) Data communication in ASCII code
The value shown below, which indicates the usage status, is converted
to an n-digit (hexadecimal) ASCII code and transmitted to the external
device side. (16 clusters/4 digits)
2) Data communication in binary code
An m-byte value that indicates the usage status is transmitted to the
external device side.
(16 clusters/2 bytes)
3) The following items are included in the free cluster table.
The usage status of each cluster is indicated by one cluster per bit.
16th cluster from
the head cluster
b15 – – – – – – b8 b7 – – – – – – b0
(Example)
0 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1
0: Free
1: Used
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Last cluster
In the usage status example shown above, the following free cluster
table is returned to the external device.
• 32 clusters are returned while communicating in ASCII code
"3CFF003F" is returned and transmitted sequentially beginning from
"3".
• 32 clusters are returned in the data communication in binary code
FF
H
beginning from FF
4) When a drive memory is defragmented, a free cluster table is not returned.
to 100 (16 to 256) is sequentially transmitted beginning from
H H
Head cluster
............ 3CFF
............ 003F
............ 0000
............ 0000
, 3C , 3F , and 00 are returned and transmitted sequentially
H H H
.
H
to 100 (16 to 256) is
H H
(Values for 16 bits)
H
H
H
H
, 20 ... in
H H
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