Grass Valley 2200 - Manual (Page 16)

2-2
Section 2 Ð Editor Protocol
Break Character
The main component of the Editor Interface protocol is a 1-1/2 character-length
Òbreak.Ó A break consists of a spacing or logical low (0) condition on the serial bus
(see Figure 2-2) followed by a minimum of two bit-times of marking (logic 1)
condition. The Bus Controller (editor) transmits a break to the switcher,
forewarning of an impending message.
The break forces all tributaries , or listeners (such as the switcherÕs editor port),
from the ÒIdleÓ state into the ÒActiveÓ state. A break can be sent only by the Edit
Controller. When the switcher receives the break, it ceases all bus
communications, resets any communication error condition, and prepares to
receive an address.
Figure 2-2. Break Character
First
Character
of Address
Byte
Marking Data
2 or More Bit Times
Spacing Data
17 to 20 Bit Times
1 Bit Time (26 µ S @ 38.4K Baud)
SMPTE Break Character
0350-07