Grass Valley 2200 - Manual (Page 18)

2-4
Section 2 Ð Editor Protocol
Address Byte
Once the break has been received, the Editor Interface advances to the active state
and begins expecting a one-byte address. The switcher will respond to the
switcher address 30H (Hexadecimal), when transmitted by the Edit controller.
After receiving the address, the Editor Interface accepts command/message block
transmissions containing commands, data requests, and other data directed
toward the switcher. As long as communication errors do not occur, the Editor
Interface can skip the break/address sequence during the remainder of the
transmissions. Command/message blocks can be sent repeatedly, one after
another, without break interruptions.
The address is one byte long and directed to a speciÞc tributary. If the received
address matches the tributaryÕs assigned address, the tributary advances to the
Selected state and awaits instructions. The address of the switcher is Þxed as 30H.
In response to the address, the 3000 transmits an acknowledgment byte of 84H to
the controller, indicating the change in status to the ÒSelectedÓ State. If an address
of 31H is received, the switcher transmits an acknowledgment byte of 84H to the
controller, but stays in the ÒActiveÓ State. If the address does not match, the
tributary drops off the bus (goes Idle) and awaits another break.
Note that when the switcher receives a break without an address as a result of an
Editor Interface reset (
RESET button pressed, or a warm or cold start of the Editor
Interface), it returns the 84H acknowledgment byte to the controller. If the edit
controller sends subsequent breaks to the switcher (when no Editor Interface reset
has occurred), the switcher responds by sending 85H followed by 84H.