Vaddio Sony EVI-D70 PTZ Camera - Manual (Page 32)

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Command List
VISCA Communication
Specifications
VISCA packet structure
The basic unit of VISCA communication is called a
packet (Fig. 2). The first byte of the packet is called
the header and comprises the sender’s and receiver’s
addresses. For example, the header of the packet sent
to the EVI-D70/P assigned address 1 from the
controller (address 0) is hexadecimal 81H. The packet
sent to the EVI-D70/P assigned address 2 is 82H. In
the command list, as the header is 8X, input the
address of the EVI-D70/P at X. The header of the reply
packet from the EVI-D70/P assigned address 1 is 90H.
The packet from the EVI-D70/P assigned address 2 is
A0H.
Some of the commands for setting EVI-D70/P units
can be sent to all devices at one time (broadcast). In
the case of broadcast, the header should be
hexadecimal 88H.
When the terminator is FFH, it signifies the end of the
packet.
Timing Chart
As VISCA Command processing can only be carried
out one time in a Vertical cycle, it takes the maximum
1V cycle time for an ACK/Completion to be returned.
If the Command ACK/Completion communication
time can be cut shorter than the1V cycle time, then
every 1V cycle can receive a Command.
From this point, if 2 or more commands in a row are to
be sent, wait for the first command (for normal
commands, an ACK or an error message, for query
commands, an Inquiry Packet) to be carried out before
sending the next one.
Query Commands
Command
16.7msec(20msec*PAL)
RxD
TxD
ACK Completion
16.7msec(20msec*PAL)
RxD
TxD
Inquiry Pocket
Command
General Commands
16 Byte
Within
Within
Fig. 2 Packet structure
Bit 7
(MSB)
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSB)
1 0
FF
Bit 7
(MSB)
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSB)
1 1 1 1 1 1 1 1
Packet (3 to 16 bytes)
Message (1 to 14 bytes) Header Terminator
Byte 1 Byte 2 Byte 3
Sender’s
address
Receiver’s address
Note
Fig. 2 shows the packet structure, while Fig. 3 shows
the actual waveform. Data flow will take place with
the LSB first.
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5
(LSB) (MSB)
Bit 6 Bit 7
Fig. 3 Actual waveform for 1 byte.
Start
bit Stop
bit.
1 byte