TANDBERG SM6610, Справочное руководство

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RS-485 Remote Control Protocol
Page 6-4 Reference Guide: SM6610, SM6615, SM6620 and SM6625 Satellite Modulators
ST.RE.E10152.2
Message Format
The protocol is based on a stream of data bytes that represent a number
of fields to form a message. All the bytes are ASCII encoded except for the
address field and checksum field. The subscripts of number indicate their
numeric base. The fields <> in a complete message are as follows:
<start> <address> <type><value><end><checksum>
Table 6.1: Message Syntax
Start
Indicates the start of a message. For messages to the Modulator this field is the ‘STX’ (ASCII 2
10
)
character. For messages from the Modulator that indicate a message error this field is the ‘NAK’
(ASCII 21
10
) character. For other messages from the Modulator this field is the ‘ACK’ (ASCII 6
10
)
character.
address
Indicates the identifying address of the destination or source device of the message. Device address
value can be from 1
10
to 127
10
inclusive. This field is 1 byte in length.
type
Specifies the type of command/response message. This field is numeric and 2 bytes in length, with
valid values.
value
Is the command/response message data. It comprises a number of sub fields. The sub fields can be
numeric or TEXT values.
End
Indicates the end of a message. This field is the ‘ETX’ (ASCII 3
10
) character.
checksum
Calculated by XOR-ing all bytes from the start field to the end field, inclusive. This field is 1 byte in
length.
Example Message
Table 6.2 shows an example of a Message sent to the Modulator.
Table 6.2: Example Message
Byte Type ASCII Char Value Description
Hex (0x) Dec
1 Start STX 2 2 Start character
2 Address A 41 65 The device address is 65
3 Type 2 24 36 The type of message
4 Type 4
5 Value F FE 254 Numeric value
6 Value E
7 Value 6 6B7 1719 Numeric value
8 Value B
9 Value 7
10 Value N Name 4 TEXT value
11 Value a
12 Value m
13 Value e
14 Value space
15 Value 4
16 End ETX 3 3 End character
17 Checksum 35 53 Checksum
The example shown in Table 6.2 sends a message to the Modulator of type
0x24.