Grass Valley 2200 - Manual (Page 80)

4-2
Section 4ÑParameter-Based Command Set
General Discussion of the Command Set
The command structure is based on the same model used throughout the
standard protocol already released:
■ Byte Count
■ Effects Address
■ Command Code
■ Message
For the PBCS command set, the Message contains two additional address
Þelds and a variable 1 to 4 bytes data Þeld (as required). The combination
of the added address Þelds with the Effects Address produces a single
address for the parameter being manipulated.
The data Þeld for the Read command does not exist, therefore, a shorter
command length is required. The response by the switcher to a Read
command is a Set command.
The data Þeld for the Set and Trim commands varies from 1 to 4 bytes. The
length of these commands varies to effect the size of the data Þeld.
Addressing
The Effects and Subsystem addresses are 1 byte each, while the Base
address is 2 bytes for a total of 4 bytes. These 4 bytes of addressing data are
combined to form the parameter and its location within the switcher
architecture.
Each speciÞc implementation of the command set, as described in this
document, details the possible effects and subsystem addresses available to
it, as well as the relevant base addresses needed to fulÞll the command's
requirement. Not all possible addresses of each type can be combined with
each other to form meaningful parameters.
Function
Byte
Count
Effects
Address
Command
Code
Subsystem
Address
Base
System
Address
(2)
Data
(1 to 4)
Read 05 EX 45 SX BX BX
Set 6 to 9 EX C5 SX BX BX 1 to 4
Trim 6 to 9 EX CB SX BX BX 1 to 4