Sony EVI-D70 Technical Manual page 31

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
Header
Sender's
address
1
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(MSB)
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.
General Commands
Command
RxD
TxD
16.7msec(20msec*PAL)
Within
Query Commands
16.7msec(20msec*PAL)
Within
Command
RxD
TxD
Packet (3 to 16 bytes)
Message (1 to 14 bytes)
Byte 1 Byte 2 Byte 3
Receiver's address
0
(LSB)
Fig.2 Packet structure
ACK Completion
Completion
16 Byte
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.
Terminator
1 1 1 1 1
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(MSB)
Command and inquiry
Command
Sends operational commands to the EVI-D70/P.
Inquiry
Used for inquiring about the current state of the
EVI-D70/P.
Command Packet
Inquiry 8X QQ RR ... FF
1) QQ = 01 (Command), 09 (Inquiry)
2)
RR = 00 (Interface), 04 (camera 1), 06 (Pan/Tilter)
X = 1 to 7: EVI-D70/P address
Command List
FF
1 1 1
(LSB)
Note
QQ 1) = Command/Inquiry,
2)
RR = category code
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