Operating instructions

User Interfaces DVB3030/DVB3030L Digital Video Broadcast Modulator
4-26 TM052 - Rev. 3.5
MPARM_FRAMING_ERROR 0x0419
MPARM_SCTSOURCE_ERROR 0x041B
MPARM_CIRCUITID_ERROR 0x0423
MPARM_INTERFACETYPE_ERROR 0x0429
MPARM_INTERFACENOTPRESENT_ERROR 0x042A
MPARM_INTERFACECOMMUNICATION_ERROR 0x042B
MPARM_SYMBOLRATE_ERROR 0x042C
MPARM_NOTIMPLEMENTED_ERROR 0x042D
MPARM_DATAPOLARITY_ERROR 0x042E
MPARM_INTERFACE_ERROR 0x042F
MPARM_SYMBOLRATEMODE_ERROR 0x0430
MPARM_FRAMINGMODE_ERROR 0x0450
MPARM_ROLLOFF_ERROR 0x0451
MDPARM_TIME_ERROR 0x0A01
MDPARM_DATE_ERROR 0x0A02
4.3.6 Collision Avoidance
When properly implemented, the physical and logical devices and ID addressing scheme of the
COMMSPEC normally precludes message packet contention on the control bus. The
importance of designating unique IDs for each device during station configuration cannot be
overemphasized. One pitfall, which is often overlooked, concerns multi-drop override IDs. All
too often, multiple devices of the same type are assigned in a direct-linked ("single-thread")
configuration accessible to the M&C computer directly. For example, if two DVB3030
Modulators with different addresses (DESTINATION IDs) are linked to the same control bus at
the same hierarchical level, both will attempt to respond to the M&C computer when the
computer generates a multi-drop override ID of 23. If their actual setup parameters, status, or
internal timing differs, they will both attempt to respond to the override simultaneously with
different information, or asynchronously in their respective message packets and response
packets, causing a collision on the serial control bus.
To preclude control bus data contention, different IDs must always be assigned to the equipment.
If two or more devices are configured for direct-linked operation, then the M&C computer and all
other devices configured in the same manner must be programmed to inhibit broadcast of the
corresponding multi-drop override ID.
The multi-drop override ID is always accepted by devices of the same type on a common control
bus, independent of the actual DESTINATION ID. These override IDs with the exception of
“BROADCAST” are responded to by all directly-linked devices of the same type causing
contention on the bus. The “BROADCAST” ID, on the other hand, is accepted by all equipment
but none of them returns a response packet to the remote M&C.
The following multi-drop override IDs are device-type specific, with the exception of
"BROADCAST". These are summarized below with ID values expressed in decimal notation: