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Byte 8: The last byte in a message with data is an Inverse Data Checksum. Sum all of the
data bytes, then take the low order eight bits of the result and invert each bit such that the
sum plus IDCHK equals FF.
Response Time
The display must initiate a response within 150 msec after receipt of a message from the
host.
Backlight Brightness Minimum Value Command (BRI) INPUT:
This command shall be sent to the display to command the backlight minimum brightness
control setting. The brightness value shall be sent as 1 byte in the DATA field. A setting of
0x00 shall indicate off. The range is 0x00 to 0xFF (0% to 100%).
Command 19% Brightness:
ATTN
ADDR
CMD0
CMD1
CMD2
LEN
IHCHK DATA IDCHK
0x07
0xFF
0x42
0x52
0x49
0x01
0x1B
0x31
0xCE
Acknowledge 19% Brightness:
ATTN
ADDR
CMD0
CMD1
CMD2
LEN
IHCHK DATA IDCHK
0x06
0xFF
0x42
0x52
0x49
0x01
0x1C
0x31
0xCE
Backlight Brightness Maximum Value Command (BRM) INPUT:
This command shall be sent to the display to command the backlight maximum brightness
control setting. The brightness value shall be sent as 1 byte in the DATA field. A setting of
0x00 shall indicate off. A setting of 0xFF shall indicate maximum brightness.
Command 70% Brightness:
ATTN
ADDR
CMD0
CMD1
CMD2
LEN
IHCHK DATA IDCHK
0x07
0xFF
0x42
0x52
0x4D
0x01
0x17
0xB4
0x4B
Acknowledge 70% Brightness:
ATTN
ADDR
CMD0
CMD1
CMD2
LEN
IHCHK DATA IDCHK
0x06
0xFF
0x42
0x52
0x4D
0x01
0x18
0xB4
0x4B
Backlight Brightness Command (BRT) INPUT:
This command shall be sent to the display to command the backlight brightness control
setting. This command is used to set the backlight brightness to the proper level
corresponding to the ECDIS color chart and illuminates the ECDIS LCD. The brightness
value shall be sent as 1 byte in the DATA field. A setting of 0x00 shall indicate off. A setting
of 0xFF shall indicate maximum brightness.
If the data checksum is valid and the brightness was set, the display shall reply to this
command with an ACK attention code. The DATA field in the reply shall indicate the
resulting brightness control setting.
Each time a “BRT” command is received by the display, the On Screen Display (OSD)
Menu is reset as follows: