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Serial Communication (SCOM) Interface
CMD 0
CMD 1
0x42
0x52
0x4D
0x41
0x56
0x45
0x50
0x4F
0x4D
0x43
0x54
0x59
0x45
0x45
*[ Note: This command is not available on pre Feb 2005 units ]
Data Length (LEN)
This byte defines the length of DATA in the message in bytes. The maximum value for this field
shall be 74 bytes. The minimum value is 0 bytes.
Inverse Header Checksum (IHCHK)
This is a simple 8-bit checksum of the header data, message bytes 0 to 5 on which a bit-wise
inversion has been performed. The checksum shall be initialised to 0. The 8-bit sum (without carry)
of bytes 0, 1, 2, 3, 4, 5 and 6 shall be 0xFF.
To any message that fails the checksum, the receiver shall reply with the attention code set to NAK
and no data field. This requirement does not apply to Broadcast messages in RS-485 mode, in
which case there will be no reply.
Data Field (DATA)
The DATA field shall only be transmitted if LEN is greater than 0. This field is dependent upon the
CMD transmitted.
Inverse Data Checksum (IDCHK)
These bytes shall only be transmitted if LEN is greater than 0. This is a simple 8-bit checksum
of the data field, message bytes 7 to 7+(LEN-1) on which a bit-wise inversion has been performed.
The checksum shall be initialised to 0. The 8-bit sum (without carry) of bytes 7 through 7+LEN
inclusive shall be 0xFF. The receiver will reply to any message that the checksum has failed with
the attention code set to NAK. This requirement does not reply to broadcast messages in RS-485
mode, in which case there will be no reply.
Message Commands
The following sections define the message formats for each of the specific commands.
Brightness Command "BRT"
This command shall be sent to the display to command the backlight brightness control setting.
The brightness value shall be sent as 1 byte in the DATA field. A setting of 0x00 will indicate off.
Communication Interface
IND100084-1
CMD 2
ASCII
Description
0x54
"BRT"
Brightness Command
0x4E
"MAN"
Manufacturer ID Code
0x52
"VER"
Display ID Version Number
0x54
"POT"
Potentiometer control
0x43
"MCC"
Display Control Command
0x50
"TYP"
Type/Model Number Command
0x43
"ETC"
Elapsed TIme Counter*
69
INB100005-3 (Rev 9)
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