evertz 5010, Инструкция по эксплуатации

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Model 5010 Time Code Master Manual
SERIAL REMOTE CONTROL PROTOCOL
Revision 3.1.1
Page 5-3
the broadcast communications state. The diagram shows the various states of the device. The
designation R( ) indicates the data received from the controller, while the designation T( ) indicates the
data transmitted by the Device.
5.3. MESSAGE BLOCK FORMAT
Once communications have been established, command messages may be sent to the Device.
Each control message starts with the STX character and ends with a checksum. The message blocks
are structured as follows:
STX BYTE COUNT MESSAGE CHECKSUM
STX:
Start of message character (02 hex)
BYTE COUNT:
Count of command message not including the STX, BYTE COUNT or CHECKSUM.
MESSAGE:
Variable length command message.
CHECKSUM:
The two's complement of the one byte sum of the MESSAGE and the BYTE COUNT.
The purpose of the checksum is to verify that all the bytes in the message that contain variable data
have been received properly. The STX is the only byte that has a fixed value, so it is the only byte not
included in the checksum calculation. The checksum is calculated by adding all the variable bytes
together. The least significant byte of this sum is then subtracted from 100 hex to compute the
checksum. To verify that the checksum is computed correctly, add all the bytes including the
checksum but excluding the STX together. The least significant byte of the sum should be zero if the
checksum is computed correctly.
The MESSAGE consists of a command and optional bytes of data and is structured as follows:
COMMAND DATA 1 ..... DATA n
COMMAND:
Single byte command directed to device.
DATA 1...DATA n:
Variable length, any arguments required by COMMAND.
If the command message was not accepted by the Device due to a checksum error, parity error or an
invalid command the Device will respond with a
NAK
(05 hex) character and re-enter the SELECT
state.
If the command message is accepted by the Device and there is no data response required, it will
respond with an
ACK
(04 hex) character and re-enter the SELECT state.
If the command message requires a data response, the Device will transmit a response message
structured as follows:
STX:
Start of message character (02 hex)
BYTE COUNT:
Count of response message not including STX, BYTE COUNT or CHECKSUM.
COMMAND ECHO:
Command message echoed
MESSAGE:
Variable length response message consisting of the data requested by the
command message.
CHECKSUM:
The two's complement of the one byte sum of the COMMAND ECHO, MESSAGE
and the BYTE COUNT.