D14640.01—MARCH 2010
21
TANDBERG PrecisionHD 1080p/720p camera
Camera User Guide
Contents
Introduction
Physical interface
Cables
Connecti to codec
Video formats
Daisy chaining
Appendices
Contact us
www.tandberg.com
The VISCA™/RS–232
control protocol
When interfacing to the PrecisionHD 12X/4X
1080p, the codec uses an RS-232 control
interface that resembles the Sony VISCA™
protocol.
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 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:
90-5Y-FF
Returned by camera when execution of
commands and inquiries are completed.
•
Error packets:
90-6Y-..-FF
Returned by camera instead of a completion
message when command or inquiry failed to
be executed.
General error messages, unless otherwise
specified:
•
90-6Y-01-FF
Message length error
(>14 bytes)
•
90-6Y-02-FF
Syntax error
•
90-6Y-03-FF
Command buffer full
•
90-6Y-04-FF
Command cancelled
•
90-6Y-05-FF
No socket (to be cancelled)
•
90-6Y-41-FF
Command not executable
•
Y = socket numbe
r
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.
The RS232 Message format
...
Sender’s
address
Receiver’s
address
1 0
LSB
Packet (3 to 16 bytes)
Message (1 to 14 bytes)
Address
Byte 1 Byte 2 Byte 3
Terminator
FF
1 1 1 1 1 1 1 1
LSB