Rotel RS-232 Service manual
Rotel RS232 Serial Bus Communication
1. 1 Byte Waveform format
5V
START
STOP
0V
2. Bus Status Test
2~10ms
MessageMessage
A. Test starts to see if line is empty for 2~10msec before transmitting new
message.
B. Line test time is fixed in 2~10msec randomly.
3. Message Structure
META Encoding
COUNT
START IDCOUNT TYPE CHKSUMDATA
CHKSUM
Start: 0xFE
• Whenever 0xFE is received this indicates the start of a new message. The
start code is always 0xFE.
Count
• This byte indicates the total number of bytes from the ID byte to the Data
byte(s).
ID
• The device ID byte of the model being controlled. The protocol for each
model will specify the correct ID.
Type
• The message type - 0x10 for Command (Transmit) messages, and 0x20 for
feedback status (Receive) messages.
Data
• The data or commands to transmit.
Checksum
• The total value of all bytes except Start. Calculate by adding each byte. In
the case that the total is larger than 2 digits, drop the most significant bit.
...
Example 1: Transmit command Volume Up to RSP 1098
0xFE 0x03 0xA0 0x10 0x0B 0xBE
Start: 0xFE Always 0xFE
Count: 0x03 Indicates 3 bytes to follow - (ID, Type, 1 Data byte)
ID: 0xA0 ID byte for RSP 1098
Type: 0x10 Indicates command type
Data: 0x0B Data value for Volume Up
Chk: 0xBE Checksum - calculate 0x03 + 0xA0 + 0x10 + 0x0B = 0xBE
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