Visca Communication Specifications; Timing Chart - Sony EVI-HD7V Technical Manual

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-HD7V/HD3V 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)
Note
Fig. 2 shows the packet structure, while Fig. 3 shows
the actual waveform. Data flow will take place with
the LSB first.

Timing Chart

As VISCA command processing can only be carried
out one time per vertical cycle, it takes the minimum
time of one V cycle for an ACK/Inquiry Packet to be
returned after the command.
Even if the transmission time between the ACK/
Inquiry Packet and the next command is shorter than
the duration of one V cycle, the command will not be
received until the ACK/Inquiry Packet is sent.
Packet (3 to 16 bytes)
Message (1 to 14 bytes)
Byte 1 Byte 2 Byte 3
0
Receiver's address
(LSB)
Fig. 2 Packet structure
Start
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5
bit
(LSB)
Fig. 3 Actual waveform for 1 byte.
sent to the EVI-HD7V/HD3V assigned address 2 is
82H. In the command list, as the header is 8X, input
the address of the EVI-HD7V/HD3V at X. The header
of the reply packet from the EVI-HD7V/HD3V
assigned address 1 is 90H. The packet from the
EVI-HD7V/HD3V assigned address 2 is A0H.
Some of the commands for setting EVI-HD7V/HD3V
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.
1 1 1 1
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(MSB)
1 byte
Stop
Bit 6 Bit 7
bit.
(MSB)
General Commands
Command
Query Commands
Command
Command List
Terminator
FF
1 1 1 1
(LSB)
ACK Completion
More than 16.7 msec
(20 msec 50 Hz system)
More than 16.7 msec
(20 msec 50 Hz system)
Inquiry Packet
16 Byte
20