Hatteland Display 20 inch - HM 20T07 MIL-H - Manual (Page 51)

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Serial Communication (SCOM) Interface
Communication Interface
IND100084-1
Data Rate
The unit is configured to transmit and receive data at 9600 bits/second.
Data Format
Data shall be transmitted with no parity, 8 data bits, one start bit, and one stop bit.
Message Format
The basic message format shall be as follows:
Byte # 0 1 2,3,4 5 6 7, etc 7+LEN
ATTN ADDR CMD LEN IHCHK DATA IDCHK
The minimum message size is 7 bytes. The maximum message size is 82 bytes, consistent with 61162-1.
Attention (ATTN)
This byte is used to identify a start of message. It can be one of 3 values:
ATTN Description
0x07
0x06
0x15
Command (ASCII BELL)
Acknowledge (ASCII ACK)
Negative Acknowledge (ASCII NAK)
A device shall send a command using the 0x07 Attention Code. The unit will respond to the command with either an
ACK if the command completed successfully, or a NAK if the command failed.
Address (ADDR)
This byte is used to specify a particular unit to receive a Command and to identify the unit responding (ACK or NAK)
to a Command. All units will support the broadcast address. The unit will meet all functional requirements without
individual unit addressing.
The Address field shall have the following values:
ADDR Description
0xFF
Broadcast - Addressed to all
units
0x00 to 0x0F
Address of a specific unit
(max of 16 units)
Command (CMD)
The command shall be one of the following values:
CMD 0 CMD 1 CMD 2 ASCII Description
0x42 0x52 0x54 “BRT” Brightness Command
0x4D 0x41 0x4E “MAN” Manufacturer ID Code
0x56 0x45 0x52 “VER” Unit ID Version Number
0x50 0x4F 0x54 “POT” Potentiometer control
0x4D 0x43 0x43 “MCC” Unit Control Command*
0x54 0x59 0x50 “TYP” Type/Model Number Command
0x45 0x45 0x43 “ETC” Elapsed TIme Counter**
*Note: This command is not available for Maritime Multi Computer (MMC) units.
**Note: This command is not available for pre Feb 2005 units