Siemens SIMATIC MV540 H - Page 116

Process interfacing via an automation system (PLC, PC)
9.3 Control with Ident profile
SIMATIC MV500
116 Operating Instructions, 06/2018, C79000-G8976-C494-01
Command: Read match string
● The "Read match string" MV command is used to prepare reading of the match string.
The actual read operation is not performed with the "PHYSICAL WRITE" command.
● The memory area of the receive data of the "PHYSICAL WRITE" command only contains
the command identifier itself.
● Send the "Read match string" command with the "PHYSICAL WRITE" command and wait
for the positive response. Then read out the actual string with a "PHYSICAL READ"
command.
● The "PHYSICAL WRITE" command must specify the length "0x01"
("CMD_STRUCT.Length = 0x01"); otherwise, the command receives a negative
acknowledgment.
Table 9- 16 CMD_STRUCT
Parameter
Value
CMD
0x71
OffsetBuffer 0x00
UID
0x00
Length
0x01
StartAddress
0x00
Table 9- 17 Memory area of the receive data (TXREF or RXREF)
Address
Value
Meaning
0x0000 0x04 Command identifier
"Read match string"
DISA bit
Command: Set DISA bit
The command data to be "written" in the "PHYSICAL WRITE" command only contains the
command identifier "Set DISA bit".
If the "DISA" bit of the optical reader has been set, the command receives positive
acknowledgment. If the "DISA" bit has already been set, it remains set.
The "PHYSICAL WRITE" command must specify the length "0x01"
("CMD_STRUCT.LEN_DATA = 0x01"); otherwise, the command receives a negative
acknowledgment.