Omron V720 Series, Руководство по эксплуатации

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Communications Commands and Responses
Section 5-3
5-25
5-3-7 General Commands and Responses
1) Special Read (RD)
If there is one Tag within the communications area, data will be read from the Tag at a speed
faster than normal reading.
Command Frame Structure
STX Node No. Command
code
“RD”
Communi-
cations
Data
type
Fixed
“0”
First read
page
No. of read
pages
ETX BCC
1 2 2 2 1 1 2 2 1 1
Communications Specifies a communications method
UT : Special Read Trigger
UA : Special Read Auto
UR : Special Read Repeat
For details, refer to 5-7 Communications Methods
Data type Specifies whether the read data is represented in ASCC or HEX.
A : ASCII code
H : HEX code
For details, refer to 5-6 Data Type
First read page
Specifies the first page in hexadecimal to read from the Tags.
Specification range: 00 to 0A
, FF
(FF can be specified only when using Philips’ block 4 as user memory. For details,
refer to 2-5 Tag Memory Map.)
No. of read page
Specifies the number of pages in hexadecimal to read from the Tags.
Specification range: 01 to 0C
Response Frame Structure
STX Node No. Retry
flag
Command
code
“RD”
Response
code
“00”
Read data ETX BCC
1 2 1 2 2
Specified
number
1 1
Response code
00 : Normal completion
For other response codes, refer to 5-10 Response Code List.
Read data
Indicates the data having been read. The number of characters of the data
is as follows.
ASCII code : No. of read pages x 4
HEX code : No. of read pages x 8
Note Although it is possible to access multiple Tags with the Special Read (RD)
Command, unlike multiple access mode (refer to 5-3-3 Multiple Access
Commands and Responses), anti-collision processing (processing to prevent
collisions between responses from Tags) is not performed for this command.
Therefore, it is not possible to read information from Tags when their re-
sponses collide. In order to compensate for this, it is necessary to send the
command from the host several times. Even with retry processing, if the
number of Tags is small, the faster baud rate means that there are cases
where using this command has advantages over using multiple access
commands.