Vaddio EVI-D80D90 Tech - Manual (Page 22)

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Command List
Fig. 3 Actual waveform for 1 byte.
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 the 1V cycle time, then
every 1V cycle can receive a Command.
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-D80N/D80P/D90N/D90P assigned address 1
from the controller (address 0) is hexadecimal 81H.
The packet sent to the EVI-D80N/D80P/D90N/D90P
assigned address 2 is 82H. In the command list, as the
header is 8X, input the address of the EVI-D80N/
D80P/D90N/D90P at X. The header of the reply packet
from the EVI-D80N/D80P/D90N/D90P assigned
address 1 is 90H. The packet from the EVI-D80N/
D80P/D90N/D90P assigned address 2 is A0H.
Some of the commands for setting EVI-D80N/D80P/
D90N/D90P 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.
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
Fig. 2 Packet structure
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
Start
bit
Stop
bit.
1 byte
Query Commands
General Commands
16 Byte
Command
ACK Completion
Within 16.msec
(20msec PAL)
Completion
Command
Within 16.msec
(20msec PAL)