VISCA Communication

Specifications

VISCA packet structure

The basic unit of VISCA communication is called a packet (Fig.1). 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 FCB-H11 assigned address 1 from the controller (address 0) is hexadecimal 81H. The packet sent to the FCB-H11 assigned address 2 is 82H. In the command

Command List

list, as the header is 8X, input the address of the FCB-H11 at X. The header of the reply packet from the FCB-H11 assigned address 1 is 90H. The packet from the FCB-H11 assigned address 2 is A0H.

Some of the commands for setting FCB-H11 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.

Packet (3 to 16 bytes)

Header

 

 

Message (1 to 14 bytes)

 

 

Terminator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Byte 1

Byte 2

Byte 3

 

 

 

FF

 

 

 

 

 

 

 

 

 

 

 

 

Sender’s

 

 

 

 

 

 

 

 

 

 

1

 

 

 

address

 

 

 

0

R

eceiver’s addr

ess

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit 7

Bit 6 Bit 5 Bit 4

Bit 3

Bit 2 Bit 1 Bit 0

(MSB)

 

 

 

 

 

 

 

 

 

 

 

 

(LSB)

1

1

1

1

1

1

1

1

 

 

 

 

 

 

 

 

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(MSB)

 

 

 

 

 

 

(LSB)

Fig. 1 Packet structure

Note

Fig. 1 shows the packet structure, while Fig. 2 shows the actual waveform. Data flow will take place with the LSB first.

1 byte

 

Start

Bit 0

Bit 1

Bit 2

Bit 3

Bit 4

Bit 5

Bit 6

Bit 7

Stop

 

 

bit

bit.

 

 

 

(LSB)

 

 

 

 

 

 

(MSB)

 

 

Fig. 2 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.

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.

General Commands

Command

ACK Completion

More than 16.7 msec (20msec 50Hz system)

Query Commands

More than 16.7 msec (20msec 50Hz system)

Command

Inquiry Packet

16 Byte

19