TANDBERG PrecisionHD 1080p/720p camera | Camera User Guide |
Contentsontents
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The VISCA™/RS–232 control protocol
When interfacing to the PrecisionHD 12X/4X 1080p, the codec uses an
VISCA message format
A particular command is recognized by the message information after the address byte.
Message Format
Commands are initiated from the host (i.e. the codec or any other external controller) to the camera.
After a camera has been issued a command, the camera will generate a response. Commands and responses (messages) have the following format:
•Address byte (1)
•Message bytes (1..14)
•Terminator byte (1)
See the illustration for details.
The RS232 Message format
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| Packet (3 to 16 bytes) |
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| Address |
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| Message (1 to 14 bytes) |
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| Terminator |
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| ... |
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| Byte 1 | Byte 2 | Byte 3 |
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| FF |
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1 |
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| 1 | 1 | 1 |
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| 1 | 1 | 1 | |
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Sender’s |
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address |
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The minimum length of any command or response is 3 bytes:
1.Address byte (1): Let us assume there is one host, i.e. the codec (the host is the unit controlling the camera). The host has address 0. The four least significant bits of the address byte contain the address of the receiver. In the case of a broadcast message, the receiver address must be set to
8.When we are operating a single camera, the address is 1. Hence, address bytes in messages from the host are 0x81, and messages from the camera to the host are 0x90 (the protocol allows for up to 7 cameras).
2.Message bytes (1..14): Any number of bytes containing the actual message information. Bytes may have any value in the range 0...254. The value 255 (i.e. hexadecimal FF) is reserved for the terminating byte.
3.Terminator byte (1): All messages must be terminated with a byte containing all 1’s, i.e. decimal
255(or hexadecimal FF).
Command and response exchange
When the camera receives a command, it responds with either:
•Completion message:
•Error packets:
Returned by camera instead of a completion message when command or inquiry failed to be executed.
General error messages, unless otherwise specified:
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•Y = socket number
A camera may contain two buffers so that two commands, including the command being executed, can be received.
NOTE: The PrecisionHD 1080p camera supports a single socket only. Consequently, the Y always assumes the value Y = 0.
Exceptions to these rules:
•An Initialize message will respond as indicated in the Table of Commands (this message is in fact a broadcast message, and any unit other than the host receiving the broadcast message must pass it on).
•Do not route commands or replies that are longer than 16 bytes through Sony cameras. The easiest way to avoid this is to put the TANDBERG cameras first in the chain. Commands and replies that are longer than 16 bytes are clearly marked below.
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