Siemens SIMATIC MV540 H - Page 122

Process interfacing via an automation system (PLC, PC)
9.3 Control with Ident profile
SIMATIC MV500
122 Operating Instructions, 06/2018, C79000-G8976-C494-01
Command: Read match string
To have the current match string returned when the "READ" command is received, the MV
command "Read match string" ("PHYSICAL WRITE" command) must be sent immediately
before. You can find more information on this subject in the section ""PHYSICAL WRITE"
commands / MV command interface (Page 112)".
After processing of the "PHYSICAL READ" command, the following data is available in the
memory area of the receive data:
If the length of the data to be read ("CMD_STRUCT.LEN_DATA") is not n + 2 bytes (n = total
length of the match string), the match string is truncated or the command data area is
padded with "0x00".
Table 9- 29 CMD_STRUCT
Parameter
Value
CMD
0x70
OFFSETBUFFER 0x00
EPCID_UID
0x00
LEN_DATA
≥ total length of the match string + 2
ADDR_TAG
0x00
Table 9- 30 Memory area of the receive data (TXREF or RXREF)
Address
Value
Meaning
0x0000 0x00 ... 0x0F Length of the total match string
(more significant byte)
0x0001 0x00 ... 0x0F Length of the total match string
(less significant byte)
0x0002
--
1st character of the match string
…
--
…
n + 2
--
nth Characters of the match string