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PRV-LX1 RS-422A Protocol
4.0 Command Block Format
The controlling device and the PRV-LX1 communicate through the interchange of command blocks. The
bytes in each command block are assigned as follows:
CMD-1
(MSD)
Data
Count
(LSD)
CMD-2 Data-1
Data-15
(MAX)
Checksum
1 Byte 1 Byte 1 Byte 1 Byte 1 Byte
• CMD-1/DATA COUNT CMD-1 is the upper 4 bits, DATA COUNT is the lower 4 bits
• CMD-2
• DATA-1 up to DATA-N, where n is the value in data count
• CHECKSUM
CMD-1
Indicates the function and direction of the command:
0 System Control (Controller -> PRV-LX1)
1 Return for 0, 2, or 4 of cmd-1 (PRV-LX1-> Controller)
2 Transport Control (Controller -> PRV-LX1)
4 Preset/Select Control (Controller -> PRV-LX1)
6 Sense Request (Controller -> PRV-LX1)
7 Sense Returned (PRV-LX1-> Controller)
E PRV-LX1 Original Command (Controller -> PRV-LX1)
F PRV-LX1 Original Return (PRV-LX1->Controller)
DATA COUNT
Indicates the number of bytes (maximum 15) inserted between CMD-2 and CHECKSUM
CMD-2
Designates the command
(refer to the Command Table for definitions)
DATA-1 to DATA-N
Data that corresponds to those indicated by the command
(refer to the Command Table for data formats)
CHECKSUM
Lower eight bits of the sum of the bytes in the command block
Communications Protocol
The controlling device initiates the communication. PRV-LX1 returns a response within 9 milliseconds.
The response may be:
• NAK + Error Data : undefined command or communications error
• COMMAND + Data : received a command that requests data
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• ACK : received a command that requests no data