Comtech EF Data MD2401 - Manual (Page 46)

MD2401 L-Band Multi Demod Installation and Operation Manual User Interfaces
MN-MD2401 4–14
Revision 7
DPARM_BUFFERCLOCKPOL_ERROR 0x0611
DPARM_INSERTMODE_ERROR 0x0612
DPARM_FRAMING_ERROR 0x0615
DPARM_OPERATINGMODE_ERROR 0x0616
DPARM_BERMEASUREPERIOD_ERROR 0x0619
DPARM_CIRCUITID_ERROR 0x061A
DPARM_TERRLOOPBACK_ERROR 0x061B
DPARM_BASELOOPBACK_ERROR 0x061C
DPARM_IFLOOPBACK_ERROR 0x061D
DPARM_INTERFACETYPE_ERROR 0x061E
DPARM_NOTIMPLEMENTED_ERROR 0x0622
DPARM_DATAINVERT_ERROR 0x0623
DPARM_SUMMARYFAULT_ERROR 0x0624
DPARM_EXTERNALEXCSOURCE_ERROR 0x0625
DPARM_BUFFERSIZEMSEC_ERROR 0x0629
DPARM_BUFFERSIZEBYTES_ERROR 0x062A
DPARM_ASYNCINTERFACETYPE_ERROR 0x0630
DPARM_BUFFERSIZEMSECBYTES_ERROR 0x0631
DPARM_IMPEDANCE_ERROR 0x0632
DPARM_INTERLEAVER_ERROR 0x0635
MDPARM_TIME_ERROR 0x0A01
MDPARM_DATE_ERROR 0x0A02
4.5.5 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 DD2401/DD2401L Demodulators 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 22. 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:
Directly-Addressed Equipment Multi-Drop Override ID
Broadcast (all directly-linked devices) 00
DMD-3000/4000, 4500 or 5000 Mod Section, DMD15 01