Command Packet Format
VM Series Displays RS232 User Guide
020-1359-00A
Page | 9
4. Communication Procedure
Send control commands from a host controller via the RS232 connection. Do not send a new
command until the previous command is acknowledged. However, if a response is not received
within 500 milliseconds, a retry may be triggered. Every valid command receives an ACK. A
command that is valid, but not supported in the current implementation, will be responded to
with NAV (Not Available). If the command buffer is corrupt, (transmission errors) the command
will be responded to with NAK. The display operates according to the received command. If the
command
is a valid “Get” command, the display responds with the requested info. If the
command is a valid “Set” command allowed, the display performs the requested operation.
Note:
For LAN control, the port number is 5000
5. Command Format
The RS232 packet format:
Header Monitor ID Category
Code0
Code1
Length
Data
Control
Data[0]
… Data[N]
Checksum
In Detail:
Number of Field
Name of Field
Description
Byte 1
Header
Header = 0xA6
Byte 2
Monitor ID
Monitor ID
Range: 1 ~ 255
Signal Mode: Display Address range from 1 to 255
Broadcast Mode: Display Address is 0, so no ACK
or Report is expected
Byte 3
Category
0x00
Byte 4
Code0 (Page)
0x00
Byte 5
Code1 (Function)
0x00
Byte 6
Length
Length has to be calculated in the following
way: Length = N + 3
Byte 7
Data Control
Data Control = 0x01 (fixed)
Byte 8 ~ Byte 44
Data[0] ~ Data[N]
This field can be also empty.
If not empty then the range of Data Size, N = 0 to
36.
Last Byte
Checksum
Checksum
Range = 0 to 255 (0xFF).
Algorithm: The EXCLUSIVE-OR (XOR) of all bytes
in the message except the checksum itself.
Checksum
= [Header] XOR [Monitor ID] XOR …
DATA[0] … XOR DATA[N]
