Subscribe – Grass Valley Switcher Products User Manual
Page 115
Switcher Products — Protocols Manual
115
Message Format
Set
The Set command is used to set a parameter to a specific value. As shown
on the following page, the Set command data consists of four fields.
The parameter ID (“PID”) is used to uniquely identify the parameter which
is to be set.
The flags field specifies how a parameter is to be set. A zero in this field
indicates that an absolute set is to be performed (i.e. the parameter is set to
the specified value) and is the only valid value for this parameter.
The device field contains a four byte identifier that further qualifies the
parameter to be set. Typically, the device field identifies which channel is to
be modified.
for a complete parameter list that includes
each parameter ID and parameter type (short, long, float, string, etc.), as
well as the devices associated with each parameter.
Subscribe
The subscribe command is used to solicit information from a device. This
information is delivered in the form of a subscription issue
1
. A subscription
issue is sent after receiving a subscription request and thereafter when the
requested information changes. As shown below, the Subscribe command
data consists of a request address, a request ID, a serial number, a
service ID, subscribe flags, and optional service specific data.
Table 106. Set Command Data
Field
Size
Value
Parameter ID
2 bytes
refer to Appendix B
Flags
2 bytes
0 = Absolute
Device
4 bytes
refer to Appendix B
Value
variable
refer to Appendix B
1.
Refer to Issue
for a complete description of a subscription issue.
Table 107. Subscribe Command Data
Field
Size
Value
Request Address
16 bytes
(not used)
Request ID
2 bytes
any (requestor’s choice)
echoed in Issue message
Serial Number
2 bytes
any (requestor’s choice)
Service ID
2 bytes
3 = Parameter Service
Flags
2 bytes
0 = normal service
1 = Subscribe Immediate
2 = Replace Service
3 = combination of 1 & 2
Service Data
variable
refer to Parameter Service below